Cobalt deposition selectivity on copper and dielectrics

ABSTRACT

A process for forming cobalt on a substrate, comprising: volatilizing a cobalt precursor of the disclosure, to form, a precursor vapor: and contacting the precursor vapor with the substrate under vapor deposition conditions effective for depositing cobalt on the substrate from the precursor vapor, wherein the vapor deposition conditions include temperature not exceeding 200° C., wherein: the substrate includes copper surface and dielectric material, e.g., ultra-low dielectric material. Such cobalt deposition process can be used to manufacture product articles in which the deposited cobalt forms a capping layer, encapsulating layer, electrode, diffusion layer, or seed for electroplating of metal thereon, e.g., a semiconductor device, flat-panel, display, or solar panel. A cleaning composition containing base and oxidizing agent components may be employed to clean the copper prior to deposition of cobalt thereon, to achieve substantially reduced defects in the deposited cobalt.

CROSS-REFERENCE TO RELATED APPLICATIONS

The benefit of priority under 35 U.S.C. § 119 of U.S. Provisional PatentApplication No. 62/050,166 filed Sep. 14, 2014, U.S. Provisional PatentApplication No. 62/107,273 filed Jan. 23, 2015, and U.S. ProvisionalPatent Application No. 62/110,078 filed Jan. 30, 2015 is hereby claimed.The disclosures of such U.S. provisional patent applications are herebyincorporated herein by reference, in their respective entireties, forall purposes.

FIELD

The present disclosure relates to cobalt precursors for precursors andprocesses for forming cobalt on substrates, e.g., in the manufacture ofsemiconductor products, flat-panel displays, and solar panels.

DESCRIPTION OF THE RELATED ART

Cobalt is finding increasing use in semiconductor manufacturing, such asin fabrication of integrated circuits in which cobalt disilicide hasbeen progressively displacing titanium silicide as feature and linewidthdimensions decrease, since it does not entail the linewidth dependentsheet resistance issues that are characteristic of titanium silicide.Cobalt also is currently under consideration as a conductive cap overcopper lines or as part of the barrier/adhesion layer liner for copperlines and contacts, as an encapsulant material, as a seed material forelectroless and electroplating processes, and as a replacement materialfor copper in wiring and interconnects of integrated circuits. Cobaltadditionally has elicited interest as a result of its magneticproperties for data storage applications and its potential forspintronics applications.

Interconnects are critical components of integrated circuitry, providingpower/ground connections and distribution of clock and other signals.Local interconnects comprise the lines that connect gates andtransistors, intermediate interconnects provide wiring within functionalblocks of integrated circuitry, and global interconnects distributeclock and other signals and provide power/ground connections for theentire integrated circuit. Interconnects increasingly are a dominantfactor in determining system performance and power dissipation ofintegrated circuits.

In the manufacture of integrated circuitry devices in which copper isused as a metallization material, cobalt liners and back end of the line(BEOL) interconnect caps have been developed for protection of copperinterconnects.

Such cobalt capping has been contemplated to enhance theelectromigration (EM) resistance of copper interconnects, and carbonylprecursors have been proposed for such capping applications. Carbonyls,however, are not optimum precursors due to the formation of CO as aby-product in the vapor deposition. Furthermore, the oxygen in thecarbonyl may react with copper and form oxide in the cobalt/copperinterface that degrades the EM resistance.

As a specific concern related to the foregoing issues in the advance ofsemiconductor technology beyond the 14 nm node, e.g., to the 7 nm and 5nm technology nodes, metal line and via fill processing face increasingchallenges to reduce interconnect metal line resistance and to establishhigh-yield void-free fill, particularly where copper is present in avia, and tantalum, tantalum nitride, ruthenium, and ruthenium alloys maybe employed as copper-diffusion barrier/liner materials in the backendprocess.

Accordingly, cobalt precursors and corresponding deposition processesare desired, which do not suffer from such deficiencies.

SUMMARY

The present disclosure relates to non-oxygen-containing cobaltprecursors that are useful for forming cobalt on substrates, e.g.,substrates comprising copper on which cobalt is to be deposited with thesubstrate also comprising dielectric material such as ultra-lowdielectric constant material on which cobalt deposition is desirablyavoided. The disclosure also relates to compositions comprising suchcobalt precursors, and processes and products related to such cobaltprecursors.

In one aspect, the disclosure relates to a process for forming cobalt ona substrate, comprising: volatilizing a cobalt precursor to form aprecursor vapor, wherein the cobalt precursor comprises a precursorselected from the group consisting of: (i) cobalt bis-diazadienecompounds whose diazadiene moieties are optionally independentlysubstituted on nitrogen and/or carbon atoms thereof with substituentsselected from the group consisting of: H; C₁-C₈ alkyl; C₆-C₁₀ aryl;C₇-C₁₆ alkylaryl; C₇-C₁₆ arylalkyl; halo; amines; amidinates:guanidinates; cyclopentadienyls, optionally substituted with C₁-C₈alkyl, amines, or halo substituents; C₁-C₈ alkoxy; hydroxyl; oximes;hydroxyamines; acetates; carbonyls; beta-diketonates; andbeta-ketoiminates; and (ii) cobalt compounds containing acetylenicfunctionality; and

contacting the precursor vapor with the substrate under vapor depositionconditions effective for depositing cobalt on the substrate from theprecursor vapor, wherein the vapor deposition conditions includetemperature not exceeding 200° C., and wherein the substrate includescopper surface and dielectric material surface

In another aspect, the disclosure relates to an article comprisingcobalt deposited on a substrate, as formed by a method comprising aprocess according to the present disclosure, as variously describedherein.

A further aspect of the disclosure relates to a method of reducingdefects in a deposited metal dial is vapor deposited on a base metal,such method comprising cleaning the base metal, prior to vapordeposition of the deposited metal thereon, with a cleaning compositioncomprising base and oxidizing agent having pH in a range of from 5 to10.

Yet another aspect of the disclosure relates to a method of reducingdefects in cobalt that is vapor deposited on copper, such methodcomprising cleaning the copper, prior to deposition of the cobaltthereon, with a cleaning composition comprising base and oxidizingagent, having pH in a range of from 5 to 10.

A further aspect of the disclosure relates to a method of reducingdefects in cobalt that is vapor deposited on tungsten, such methodcomprising cleaning the tungsten, prior to deposition of the cobaltthereon, with a cleaning composition comprising etchant, oxidizingagent, and optionally corrosion inhibitor, having pH in a range of from0 to 4.

In another aspect, the disclosure relates to a method of reducingdefects in a deposited cobalt that is vapor deposited on a base metal,wherein the cobalt is deposited by a process of the present disclosure,such method comprising cleaning the base metal, prior to vapordeposition of the deposited cobalt thereon, wherein the cleaningcomprises (i) contacting the base metal with a cleaning compositioncomprising base and oxidizing agent, having pH in a range of from 5 to10; (ii) contacting the base metal with a cleaning compositioncomprising etchant, oxidizing agent, and optionally corrosion inhibitor,having pH in a range of from 0 to 4; (iii) treating the base metal withhydrogen plasma; or (iv) treating the base metal with hydrogen fluoride.

Yet another aspect of the disclosure relates to a method of formingdeposited cobalt on a substrate, wherein prior to vapor deposition ofcobalt on the substrate, the substrate is cleaned with a cleaningcomposition selected from among (i) cleaning compositions comprisingbase and oxidizing agent, having pH in a range of from 5 to 10, and (ii)cleaning compositions comprising etchant, oxidizing agent, andoptionally corrosion inhibitor, having pH in a range of from 0 to 4,wherein the cleaning of the substrate is effective for at least one of(a) reducing defectivity of the deposited cobalt, (b) removing CF_(X)components from the substrate, and (c) removing or pulling back TiNpresent on the substrate.

A further aspect of the disclosure relates to a via fill process,comprising vapor depositing cobalt in a via for fill thereof, whereinthe cobalt is vapor deposited over a copper surface in the via. Anotheraspect of the disclosure relates to a void-free filled via as formed bysuch a process.

A further aspect of the disclosure relates to a process for formingcobalt on a substrate comprising metal-containing surface and oxidematerial surface, the process comprising contacting the substrate, undervapor deposition conditions effective for depositing cobalt on thesubstrate, with vapor of a cobalt precursor that is effective under thevapor deposition conditions to selectively deposit cobalt on themetal-containing surface of the substrate but not the oxide materialsurface of the substrate.

Other aspects, features and embodiments of the disclosure will be morefully apparent from the ensuing description and appended claims.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a thermogravimetric and differential scanning calorimetry plotfor Co(tBuNCHCHNtBu)₂, showing a T₅₀ value of 221.9° C., and a residualmass value of 0.2% at temperature of 772.3° C. for such cobaltprecursor.

FIG. 2 is an XRD plot for cobalt material deposited on a substrate froma Co(tBuNCHCHNtBu)₂ precursor.

FIG. 3 is a micrograph of deposited cobalt material deposited at athickness of 25.1 Å and pressure of 30 torr from a Co(tBuNCHCHNtBu)₂precursor.

FIG. 4 is a micrograph of deposited cobalt material, deposited at athickness of 69.7 Å and pressure of 30 torr from a Co(tBuNCHCHNtBu)₂precursor.

FIG. 5 is a micrograph of deposited cobalt material, deposited at acobalt thickness of 13.6 Å and pressure of 10 torr from aCo(tBuNCHCHNtBu)₂ precursor.

FIG. 6 is a micrograph of deposited cobalt material deposited at athickness of 59.3 Å and pressure of 10 torr from a Co(tBuNCHCHNtBu)₂precursor.

FIG. 7 is a micrograph of a cobalt film formed on a ruthenium substrateat a deposition pressure of 10 torr.

FIG. 8 is a plot of percentage resistivity after annealing, as afunction of annealing temperature, in degrees Centigrade, for annealingcarried out at a pressure of 30 torr and hydrogen flow-rate of 0.5 L perminute for a cobalt film formed from a Co(tBuNCHCHNtBu)₂ precursor.

FIG. 9 shows XRD plots for the cobalt films on tantalum nitride,titanium nitride, and copper substrates, in intensity (arbitrary units)as a function of the two-theta angle, in degrees.

FIG. 10 is an XRD plot of a cobalt film deposited from theCo(tBuNCHCHNtBu)₂ precursor on a tantalum nitride substrate, inarbitrary intensity units as a function of the two-theta angle, indegrees.

FIG. 11 is an XRD plot of a cobalt film deposited from theCo(tBuNCHCHNtBu)₂ precursor, in arbitrary intensity units as a functionof the two-theta angle, in degrees. The cobalt film trace on a tungstennitride (WN) substrate in this plot is the upper trace, the cobalt filmtrace on an iridium substrate is the middle trace, and the cobalt filmtrace on a tantalum substrate is the lower trace.

FIG. 12 is an XRD plot of a cobalt film deposited from theCo(tBuNCHCHNtBu)₂ precursor on an iridium oxide substrate, in arbitraryintensity units as a function of the two-theta angle, in degrees. Theiridium oxide substrate is shown as the lower trace in this plot.

FIG. 13 is an XRD plot of a cobalt film deposited from theCo(tBuNCHCHNtBu)₂ precursor on a tantalum substrate, in arbitraryintensity units as a function of the two-theta angle, in degrees. Thetantalum substrate is shown as the lower trace in this plot.

FIG. 14 is an XRD plot of a cobalt film deposited from theCo(tBuNCHCHNtBu)₂ precursor on a ruthenium substrate, in arbitraryintensity units as a function of the two-theta angle, in degrees. Theruthenium substrate is shown as the lower trace in this plot.

FIG. 15 is a scanning electron micrograph of a cobalt film depositedfrom the Co(tBuNCHCHNtBu)₂ precursor on a tantalum substrate. The cobaltfilm had a thickness of 124.6 Å.

FIG. 16 is a scanning electron micrograph of a cobalt film on a coppersubstrate, at a cobalt film thickness of 230.4 Å.

FIG. 17 is a scanning electron micrograph of a cobalt film depositedfrom the Co(tBuNCHCHNtBu)₂ precursor on a tantalum nitride substrate,wherein the cobalt film had a thickness of 188.3 Å.

FIG. 18 is a scanning electron micrograph of a cobalt film depositedfrom the Co(tBuNCHCHNtBu)₂ precursor on a titanium nitride substrate,wherein the cobalt film had a thickness of 180.1 Å.

FIG. 19 is a scanning electron micrograph of a cobalt film depositedfrom the Co(tBuNCHCHNtBu)₂ precursor on a silicon substrate, wherein thecobalt film had a thickness of 25.3 Å.

FIG. 20 is a scanning electron micrograph of a cobalt film depositedfrom the Co(tBuNCHCHNtBu)₂ precursor on a fluorine free tungsten (FFW)substrate. The cobalt film thickness was 208.7 Å, and the film had aresistivity of 91.7 μΩ-cm.

FIG. 21 is a scanning electron micrograph, at 50,000× magnification, ofa cobalt film deposited from the Co(tBuNCHCHNtBu)₂ precursor on aniridium dioxide substrate. The cobalt film had a thickness of 204.1 Å.

FIG. 22 is a scanning electron micrograph, at 200,000× magnification, ofthe cobalt film of FIG. 21, deposited from the Co(tBuNCHCHNtBu)₂precursor on an iridium dioxide substrate, wherein the cobalt film had athickness of 204.1 Å.

FIG. 23 is an XRD plot of a cobalt film deposited from theCo(tBuNCHCHNtBu)₂ precursor on a ruthenium substrate, in arbitraryintensity units as a function of the two-theta angle, in degrees. Thelower line in this plot shows the data for deposition at 290° C., andcobalt film thickness of 166 Å. The middle line in this plot shows thedata for deposition at 250° C., and cobalt film thickness of 205.1 Å.The upper line in this plot shows the data for deposition at 200° C.,and cobalt film thickness of 211.8 Å.

FIG. 24 is a graph of resistivity, in μΩ-cm, as a function of filmthickness in Ångströms, as determined by x-ray fluorescence, for acobalt film deposited from the Co(tBuNCHCHNtBu)₂ precursor on aruthenium substrate, showing the data for deposition at a temperature of200° C., 250° C., and 290° C. The data show that the cobalt film had aresistivity on the order of 30 μΩ-cm.

FIG. 25 is an XRD plot of a cobalt film deposited from theCo(tBuNCHCHNtBu)₂ precursor on a fluorine-free tungsten substrate, inarbitrary intensity units as a function of the two-theta angle, indegrees. The upper line in this plot shows the data for deposition at290° C., and cobalt film thickness of 208.7 Å. The lower line in thisplot shows the data for deposition at 250° C., and cobalt film thicknessof 127.4 Å.

FIG. 26 is a graph of resistivity, in μΩ-cm, as a function of filmthickness in Ångströms, as determined by x-ray fluorescence, for acobalt Film deposited from the Co(tBuNCHCHNtBu)₂ precursor on afluorine-free tungsten nitride substrate, at temperatures of 200° C.,250° C., and 290° C. The deposition was carried out at pressure of 30torr, and with hydrogen co-reactant flow rate of 0.5 L per minute.

FIG. 27 is a graph of resistivity, in μΩ-cm, as a function of filmthickness in Ångströms, as determined by x-ray fluorescence, for acobalt film deposited from the Co(tBuNCHCHNtBu)₂ precursor on afluorine-free tungsten nitride substrate, at a temperature of 250° C.,and precursor flow rate of 50 μmole/minute. A first run was carried outat pressure of 10 torr, and co-reactant hydrogen flow rate of 3 L perminute. A second run was carried out at pressure of 30 torr, andhydrogen co-reactant flow rate of 0.5 L per minute. A third run wascarried out at pressure of 30 torr, and hydrogen co-reactant flow rateof 3 L per minute. A fourth run was carried out at pressure of 10 torr,and hydrogen co-reactant flow rate of 0.5 L per minute.

FIG. 28 is a scanning electron micrograph of a cobalt film depositedfrom the Co(tBuNCHCHNtBu)₂ precursor on a fluorine-free tungstensubstrate, in which the film was deposited at temperature of 200° C.,pressure of 30 torr, co-reactant hydrogen flow of 0.5 L per minute,yielding a cobalt film thickness of 49.8 Å.

FIG. 29 is a scanning electron micrograph of a cobalt film depositedfrom the Co(tBuNCHCHNtBu)₂ precursor on a fluorine-free tungstensubstrate, in which the film was deposited at temperature of 250° C.,pressure of 10 torr, co-reactant hydrogen flow of 3 L per minute,yielding a cobalt film thickness of 39.8 Å, and film resistivity of 139μΩ-cm.

FIG. 30 is a scanning electron micrograph of a cobalt film depositedfrom the Co(tBuNCHCHNtBu)₂ precursor on a fluorine-free tungstensubstrate, in which the film was deposited at temperature of 250° C.,pressure of 30 torr, co-reactant hydrogen flow of 3 L per minute,yielding a cobalt film thickness of 35.8 Å, and a film resistivity of169 μΩ-cm.

FIG. 31 is a micrograph of a cobalt film deposited from theCo(tBuNCHCHNtBu)₂ precursor on a copper substrate, at depositiontemperature of 200° C., yielding a cobalt film thickness of 169.5 Å.

FIG. 32 is a micrograph of a cobalt film deposited from theCo(tBuNCHCHNtBu)₂ precursor on a copper substrate, at depositiontemperature of 150° C., yielding a cobalt film thickness of 97.6 Å.

FIG. 33 is a graph of 400° C. RTN resistivity data for cobalt filmsdeposited from the Co(tBuNCHCHNtBu)₂ precursor, and from other cobaltprecursors, on fluorine-free substrates, as a function of XRF-determinedfilm thickness. The additional cobalt precursors were: dicobalthexacarbonyl tert-butylacetylene, which has the formulaCo₂((CO)₆(HCC(CH₃)₃), with a boiling point of 52° C. at 0.8 torr (106.7Pa), existing as a red liquid at 25° C. (CCTBA); high purity CCTBA (HPCCTBA); dicobalt hexacarbonyl trimethylsilyl acetylene (CCTMSA); cobaltcarbonyl bis(trimethylsilyl acetylene, having the formula[((H₃C)Si)C≡C]₂Co(CO) (CCBTMSA); bis(N-methylacetamidinato)cobalt(Co(Methyl-Amidinate)); and bis(N-ethylacetamidinato)cobalt(Co(Ethyl-Amidinate)).

FIG. 34 is an XRD plot of a crystalline cobalt film deposited at 150° C.from the Co(tBuNCHCHNtBu)₂ precursor, in arbitrary intensity units, as afunction of the two-theta angle, in degrees.

FIG. 35 is a scanning electron micrograph of a cobalt film having athickness of 39.9 Å, which was deposited from the Co(tBuNCHCHNtBu)₂precursor on a substrate at a deposition rate of 150 μmoles per minute,at a pressure of 30 torr and a co-reactant hydrogen flow rate of 3 L perminute.

FIG. 36 is a scanning electron micrograph of a cobalt film having athickness of 13.4 Å, which was deposited from the Co(tBuNCHCHNtBu)₂precursor on a substrate at a deposition rate of 150 μmoles per minute,at a pressure of 10 torr and a co-reactant hydrogen flow rate of 3 L perminute.

FIG. 37 is an electron micrograph at a magnification of 25,000 times,showing a cobalt film that has been deposited on copper that has notbeen cleaned by a pre-deposition cleaning with the cleaning compositionof the present disclosure.

FIG. 38 is an electron micrograph at a magnification of 25,000 times,showing a cobalt film that has been deposited on copper that has beencleaned with a cleaning composition of the present disclosure,comprising an approximate weight percentage composition of 89% deionizedwater, 9% oxidizing agent, and 2% base, based on total weight of thecleaning composition, as contacted with the copper for 2 minutes at 50°C.

FIG. 39 is a schematic representation of a dual Damascene test structureutilized for cobalt deposition in accordance with the presentdisclosure, in a specific embodiment thereof.

FIG. 40 is a top view micrograph of a via test structure prior to cobaltselective growth and fill.

FIG. 41 is a cross-sectional view of the via test structure of FIG. 40.

FIG. 42 is a scanning electron micrograph (SEM) of the cross-section ofthe cobalt filled via test structure, in which cobalt completely fillsthe ˜135 nm tall and 45 nm diameter (3:1 aspect ratio) via structure.

FIG. 43 is an SEM top view of the cobalt filled via test structure whosecross-sectional view is shown in FIG. 42.

DETAILED DESCRIPTION

The present disclosure relates to non-oxygen-containing cobaltprecursors that are useful for forming cobalt on substrates insurface-selective deposition processes, e.g., deposition on substratescomprising copper on which cobalt is to be deposited with the substratealso comprising dielectric material such as ultra-low dielectricconstant material on which cobalt deposition is desirably avoided.

The disclosure further relates to compositions comprising theaforementioned non-oxygen-containing cobalt precursors, andsurface-selective deposition processes utilizing such precursors andcompositions, as well as to microelectronic products, flat paneldisplays, and solar panels, and component structures therefor, producedusing such precursors and precursor compositions.

As used herein and in the appended claims, the singular forms “a”,“and”, and “the” include plural referents unless the context clearlydictates otherwise.

As used herein, the term “film” refers to a layer of deposited materialhaving a thickness not exceeding 10 micrometers, e.g., from such valuedown to atomic monolayer thickness values. In various embodiments, filmthicknesses of deposited material layers in the practice of thedisclosure may for example not exceed 5 micrometers, or not exceed 1micrometer, or in various thin film regimes be below 200, 10 or 1nanometer(s) film thickness, depending on the specific applicationinvolved, however it will be recognized that cobalt-containing materialin the broad practice of the present disclosure may have any suitablethickness for tire application that is involved.

As used herein, the term “cobalt” is intended to be broadly construed toinclude elemental cobalt, as well as cobalt-containing compounds,mixtures, and alloys.

As used herein, the identification of a carbon number range, e.g., inC₁-C₁₂ alkyl, is intended to include each of the component carbon numbermoieties within such range, so that each intervening carbon number andany other stated or intervening carbon number value in that statedrange, is encompassed, it being further understood that sub-ranges ofcarbon number within specified carbon number ranges may independently beincluded in smaller carbon number ranges, within the scope of theinvention, and that ranges of carbon numbers specifically excluding acarbon number or numbers are included in the invention, and sub-rangesexcluding either or both of carbon number limits of specified ranges arealso included in the invention. Accordingly, C₁-C₁₂ alkyl is intended toinclude methyl, ethyl, propyl, butyl, pentyl, hexyl, heptyl, octyl,nonyl, decyl, undecyl and dodecyl, including straight chain as well asbranched groups of such types. It therefore is to be appreciated thatidentification of a carbon number range, e.g., C₁-C₁₂, as broadlyapplicable to a substituent moiety, enables, in specific embodiments ofthe invention, the carbon number range to be further restricted, as asub-group of moieties having a carbon number range within the broaderspecification of the substituent moiety. By way of example, the carbonnumber range C₁-C₁₂ alkyl, may be more restrictively specified, inparticular embodiments of the invention, to encompass sub-ranges such asC₁-C₄ alkyl, C₂-C₈ alkyl, C₂-C₄ alkyl, C₃-C₅ alkyl, or any othersub-range within the broad carbon number range.

The precursors of the invention may be further specified in specificembodiments by provisos or limitations excluding specific substituents,groups, moieties or structures, in relation to various specificationsand exemplifications thereof set forth herein. Thus, the inventioncontemplates restrictively defined compositions, e.g., a compositionwherein R^(i) is C₁-C₁₂ alkyl, with the proviso that R^(i)≠C₄ alkyl whenR^(j) is silyl.

“Aryls” as used herein includes hydrocarbons derived from benzene or abenzene derivative that are unsaturated aromatic carbocyclic groups offrom 6 to 10 carbon atoms. The aryls may have a single or multiplerings. The term “aryl” as used herein also includes substituted aryls.Examples include, but are not limited to phenyl, naphthyl, xylene,phenylethane, substituted phenyl, substituted naphthyl, substitutedxylene, substituted phenylethane and the like.

As used herein, the term “ultra-low” in reference to dielectric constantmeans a dielectric constant that is below 2.5.

The precursors of the invention can be supplied in any suitable form forvolatilization to produce the precursor vapor for deposition contactingwith the substrate, e.g., in a liquid form that is vaporized or as asolid that is dissolved or suspended in a solvent medium for flashvaporization, as a sublimable solid, or as a solid having sufficientvapor pressure to render it suitable for vapor delivery to thedeposition chamber, or in any other suitable form.

When solvents are employed for delivery of the precursors of theinvention, any suitable solvent medium can be employed in which theprecursor can be dissolved or dispersed for delivery. By way of example,the solvent medium may be a single-component solvent or a multicomponentsolvent mixture, including solvent species such as C₃-C₁₂ alkanes,C₂-C₁₂ ethers, C₆-C₁₂ aromatics, C₁₀-C₂₅ arylalkanes, C₁₀-C₂₅arylcyloalkanes, and further alkyl-substituted forms of aromatic,arylkane and arylcyloalkane species, wherein the further alkylsubstituents in the case of multiple alkyl substituents may be the sameas or different from one another and wherein each is independentlyselected from C₁-C₈ alkyl. Illustrative solvents include amines, ethers,aromatic solvents, glymes, tetraglymes, alkanes, alkyl-substitutedbenzene compounds, benzocyclohexane (tetralin), alkyl-substitutedbenzocyclohexane and ethers, with tetrahydrofuran, xylene,1,4-tertbutyltoluene, 1,3-diisopropylbenzene dimethyltetralin, octaneand decane being potentially useful solvent species in specificapplications. In one embodiment, the solvent is selected from amongtertiary amines, ethers and aromatic solvent.

The non-oxygen-containing cobalt precursors of the present disclosureinclude

Co(tBuNCHCHNtBu)₂, also referred to herein as Co(tBuDAD)₂ orCo-diazadiene, and cobalt precursors with mono- or bis-substitutedalkyl-1,3-diazabutadienyl ligands, as usefully employed in selectivesurface deposition processes in accordance with the present disclosure.

It has been discovered by the present inventors that Co(tBuDAD)₂provides a perfect selectivity of cobalt coating on copper versusdielectric surface, i.e., enabling cobalt to be deposited only on coppersurfaces but not on ultra-low dielectric constant (ULK) materialsurfaces when copper and ULK dielectric surfaces of a substrate areconcurrently contacted with Co(tBuDAD)₂ precursor vapor, when thecontacting is carried out at temperature not exceeding 200° C., e.g., attemperature in a range of from 130° C. to 200° C. Deposition of cobaltusing such Co(tBuDAD)₂ precursor at temperature in the upper portion ofsuch range, such as at temperature of 180° C. to 200° C. can be carriedout with deposition rates of greater than 1 nm/minute. When utilizinglower temperatures for such contacting, such as 150° C., the sameselectivity of copper surfaces versus ULK material surfaces can beachieved, albeit at lower deposition rates, as for example a depositionrate of ˜0.5 nm/minute, on the copper surface.

The present disclosure more generally contemplates the use of cobaltprecursors with mono- or bis-substituted alkyl-1,3-diazabutadienylligands can be employed in selective surface deposition processes.

Cobalt precursors of the general formula {RNCHCHNR}₂Co, or{R′NCRCRNR′}₂Co, wherein each R and R′ is independently selected fromamong C₁-C₈ alkyl can be utilized for deposition in atomic layerdeposition (ALD) and chemical vapor deposition (CVD) processes in thebroad practice of the present disclosure, as can mono-substituted C₁-C₈alkyl-1,3-diazabutadienyl cobalt complexes, containing other ligands,e.g., ligands selected from the following: halides, alkoxides,dialkoxides, amides, diamides, imides, oximes, hydroxylamines,amidinates, guanidinates, acetates, carbonyls, alkyls,cyclopentadienyls, beta-diketonates, and betaketoiminates. As discussedhereinabove, in various applications involving capping of coppermetallization, oxygen-containing ligands are desirably avoided, however,in other applications contemplated by the present application, such oxicligands may be usefully employed in corresponding cobalt precursors,such as in the ALD or CVD deposition of cobalt oxide, cobalt nitride,cobalt carbide, cobalt silicide, or other cobalt alloy thin films. Thedisclosure in other aspects contemplates cobalt precursors containingacetylene groups. Other cobalt precursors that can be used in the broadpractice of the present invention, e.g., to form cobalt capping layerson copper comprised in substrates also including dielectric surface,particularly ultra-low dielectric material surfaces, include the cobaltcompounds disclosed in U.S. Patent Application Publication 20130164456published Sep. 27, 2013 in the name of Charles H. Winter, et al. andWinter, et al Organometallics 2011, 30, p. 5010.

The diazadiene (DAD)-based cobalt compounds of the present disclosurecan be synthesized as described in U.S. Patent Application Publication20130251903 published Sep. 26, 2013 in the name of Won Seok Han. Othercobalt precursors described herein can be synthesized within the skillof the art based on the disclosure herein.

Accordingly, in one aspect, the disclosure relates to a process forforming cobalt on a substrate, comprising:

volatilizing a cobalt precursor to form a precursor vapor, wherein thecobalt precursor comprises a precursor selected from the groupconsisting of: (i) cobalt bis-diazadiene compounds whose diazadienemoieties are optionally independently substituted on nitrogen and/orcarbon atoms thereof with substituents selected from the groupconsisting of: H; C₁-C₈ alkyl; C₆-C₁₀ aryl; C₇-C₁₆ alkyl aryl; C₇-C₁₆arylalkyl; halo; amines, amidinates; guanidinates; cyclopentadienyls,optionally substituted with C₁-C₈ alkyl, amines, or halo substituents;C₁-C₈ alkoxy; hydroxyl; oximes; hydroxyamines; acetates; carbonyls;beta-diketonates; and beta-ketoiminates; and (ii) cobalt compoundscontaining acetylenic functionality; andcontacting the precursor vapor with the substrate under vapor depositionconditions effective for depositing cobalt on the substrate from theprecursor vapor, wherein the vapor deposition conditions includetemperature not exceeding 200° C., and wherein the substrate includescopper surface and dielectric material surface.

In specific embodiments of such process, the cobalt precursor comprisesa precursor selected from the group consisting of (i) cobaltbis-diazadiene compounds whose diazadiene moieties are optionallyindependently substituted on nitrogen and/or carbon atoms thereof withsubstituents selected from the group consisting of: H; C₁-C₈ alkyl;C₆-C₁₀ aryl; C₇-C₁₆ alkylaryl; C₇-C₁₆ arylalkyl; halo; amines;amidinates; guanidinates; cyclopentadienyls, optionally substituted withC₁-C₈ alkyl, amines, or halo substituents; C₁-C₈ alkoxy; hydroxyl;oximes; hydroxyamines; acetates; carbonyls; beta-diketonates; andbeta-ketoiminates.

In other embodiments, the cobalt precursor comprises a precursorselected from the group consisting of (i) cobalt bis-diazadienecompounds whose diazadiene moieties are optionally independentlysubstituted on nitrogen and/or carbon atoms thereof with substituentsselected from the group consisting of: H; C₁-C₈ alkyl; C₆-C₁₀ aryl;C₇-C₁₆ alkylaryl; C₇-C₁₆ arylalkyl; halo; amines; amidinates;guanidinates; cyclopentadienyls, optionally substituted with C₁-C₈ alkylamines, or halo substituents.

In yet other embodiments, the cobalt precursor comprises

In still other embodiments of the process, the cobalt precursorcomprises a cobalt precursor of the formula {RNCHCHNR}₂Co, or{R′NCRCRNR′}₂Co, wherein each R and R′ is independently selected fromamong C₁-C₈ alkyl.

The process may comprise in additional embodiments the cobalt precursorcomprising a cobalt compound containing acetylenic functionality, e.g.,wherein the cobalt precursor comprises a cobalt compound selected fromthe group consisting of dicobalt hexacarbonyl tert-butylacetylene;dicobalt hexacarbonyl trimethylsilyl acetylene; and cobalt carbonylbis(trimethylsilyl acetylene.

The dielectric material in the process of the disclosure may comprise anultra-low k dielectric material.

In various embodiments, the process of the disclosure is characterizedby one or more of the following features or characteristics: beingconducted to cap a copper metallization element on the substrate; mixingthe precursor vapor with hydrogen for the contacting; further comprisingannealing the cobalt deposited on the substrate, e.g., involving rapidthermal annealing; conducting the contacting at temperature in a rangeof from 60° C. to 200° C., or at temperature in a range of from 130° C.to 200° C., e.g., at temperature in a range of from 180° C. to 200° C.,and a cobalt deposition rate of greater than 1 nm/minute: conducting theprocess with a cobalt precursor with mono- or bis-substitutedalkyl-1,3-diazabutadienyl ligands; conducting the contacting in an ALDprocess; conducting the contacting in a CVD process; conducting thecontacting to deposit cobalt on the substrate to form a cobalt compoundthereon, wherein the cobalt compound is selected from the groupconsisting of cobalt oxide, cobalt nitride, cobalt carbide, cobaltsilicide, and mixtures thereof; wherein the deposited cobalt forms anelectrode; wherein the substrate comprises a gate or capacitorstructure; wherein the deposited cobalt forms a capping layer, e.g.,overlying a copper structure or via; wherein the deposited cobalt formsan encapsulating layer, e.g., covering a copper interconnect element;wherein the deposited cobalt forms of diffusion layer; wherein thedeposited cobalt forms a seed for electroplating of metal thereon;wherein the vapor deposition conditions comprise a deposition pressurein a range of from 2 to 1200 torr; wherein the vapor depositionconditions comprise a deposition pressure in a range of from 5 to 100torr; wherein the cobalt precursor is volatilized by vaporization of asolvent solution thereof, such as where the solvent in the solventsolution comprises an organic solvent, or a hydrocarbon solvent, or aC₄-C₁₀ alkane solvent, e.g., octane; wherein the precursor vapor istransported in a carrier gas for the contacting thereof with thesubstrate, as for example a gas selected from the group consisting ofargon, neon, xenon, krypton, helium, and hydrogen; wherein thecontacting of the precursor vapor with the substrate is conducted for aperiod of from 2 to 60 minutes; further comprising annealing the cobaltdeposited on the substrate by thermal annealing at temperature in arange of from 200° C. to 600° C., or a range of from 350° C. to 550° C.,or wherein the thermal annealing is conducted for a period of timesufficient to reduce resistivity of the deposited cobalt, by an amountin a range of from 25% to 90% of the as-deposited resistivity of thecobalt film; wherein the contacting of the precursor vapor with thesubstrate is carried out for a period of time sufficient to depositcobalt on the substrate at a thickness in a range of from 2 nm to 1000;wherein the cobalt deposited on the substrate has a resistivity in arange of from 7 to 48 μΩ-cm, or a resistivity in a range of from 10 to40 μΩ-cm; and wherein the cobalt is deposited on the substrate as a filmthereon.

The disclosure relates in various other aspects to an article comprisingcobalt deposited on a substrate, as formed by a method comprising aprocess as variously described herein, in any of the embodiments hereindisclosed. The article may for example comprise a semiconductor device,flat-panel display, or solar panel. In specific embodiments, thedeposited cobalt may comprise an electrode. In other embodiments, thearticle may comprise a gate of capacitor structure. In still otherembodiments, the deposited cobalt may form a capping layer, e.g.,overlying a via. The deposited cobalt in other embodiments may form anencapsulating layer, e.g., covering a copper interconnect element. Thedeposited cobalt in other embodiments may form a diffusion barrier inthe article. In still further embodiments, the deposited cobalt may forma seed for electroplating of metal thereon.

It will be recognize that the process and article of the presentdisclosure may be constituted, embodied, and implemented, in any of hervariety of suitable manners, as will be apparent to those of ordinaryskill in the art, based on the disclosure herein.

Thus, in various aspects, the present disclosure relates to a processfor forming cobalt on a substrate, comprising: volatilizing a cobaltprecursor of the disclosure, to form a precursor vapor; and contactingthe precursor vapor with the substrate under vapor deposition conditionseffective for depositing cobalt on the substrate from the precursorvapor, wherein the vapor deposition conditions include temperature notexceeding 200° C., wherein the substrate includes copper surface anddielectric material, e.g., ultra-low dielectric material.

In various embodiments of such process, the cobalt precursor isvolatilized by vaporization of a solvent solution thereof. The solventsolution may for example comprise an organic solvent, such as ahydrocarbon solvent, e.g., a solvent selected from the group consistingof alkane solvents, aromatic solvents, ketone solvents, ether solvents,etc. In various embodiments, the solvent may comprise an alkane solvent,e.g., a C₄-C₁₀ alkane solvent, such as butane, pentane, hexane, heptane,octane, nonane, or decane, or, more generally, any other solventspecies, solvent mixture, etc. that is compatible with foe cobaltprecursor.

The process of the present disclosure may be conducted, in variousembodiments, with the precursor vapor being transported in a carrier gasto the contacting step in which the precursor vapor/carrier gas mixtureis contacted with the substrate to effect deposition of cobalt on thesubstrate. The carrier gas may be of any suitable type, and may includeany suitable carrier gas or gases that are compatible with the precursorvapor. The carrier gas may for example comprise an inert or othersuitable gas, such as argon, neon, xenon, krypton, helium, hydrogen,etc.

The vapor deposition conditions in the above-described process may invarious embodiments comprise pressure in a suitable range, e.g., a rangeof from 2 to 1200 torr, a range of from 2 to 100 torr, a range of from 5to 100 torr, a range of from 5 to 70 torr, a range of from 10 to 50Torr, or pressure in other suitable pressure range. The vapor depositionconditions in various embodiments may comprise temperature in a range offrom 25° C. to 200° C., a range of from 60° C. to 200° C., a range offrom 100° C. to 200° C., a range of from 120° C. to 175° C., a range offrom 125° C. to 165° C., or temperature in other suitable temperaturerange.

The cobalt precursor vapor may be mixed with co-reactants and/or carriergases, for delivery to the contacting of the precursor vapor with thesubstrate. The substrate may be of any suitable type that includescopper surface and dielectric material surface, and may for examplecomprise a semiconductor substrate, such as a silicon oxide substrate, ametal substrate, or a glass, ceramic, or other appropriate substrate forthe specific product to be formed comprising the cobalt film, whichincludes such copper and dielectric surface.

The contacting of the precursor vapor with the substrate in processes ofthe disclosure may be carried out for any suitable period of time, e.g.,a period of from 2 to 60 minutes, a period of from 3 to 15 minutes, aperiod of from 5 to 12 minutes, or other suitable period of time. Invarious embodiments, the contacting is conducted for a period of timesufficient to deposit a predetermined thickness of the deposited cobalt.Such thickness may be of any suitable magnitude, e.g., a thickness in arange of from 2 nm to 1000 nm, a thickness in a range of from 2 nm to500 nm, a thickness in a range of from 4 nm to 400 nm, a thickness in arange of from 5 nm to 300 nm, or thickness in other thickness range.

In various embodiments, the cobalt film after the contacting is annealedby a thermal annealing process. The thermal annealing can be carried outat any suitable annealing conditions, e.g., temperature in a range offrom 200° C. to 600° C., a range of from 200° C. to 550° C. a range offrom 350° C. to 550° C., a range of from 375° C. to 450° C., ortemperature in other suitable temperature range.

In various embodiments of the process of the present disclosure, thethermal annealing can be conducted for a suitable period of time toachieve a desired resistivity, sheet resistance, and/or other desiredcharacteristics of the film. For example, the annealing can be carriedout for a period in a range of from 1 minute to 20 minutes, in a rangeof from 2 minutes to 15 minutes, in a range of from 10 to 12 minutes, orother period of time. The thermal annealing may be conducted for aperiod that is effective to reduce resistivity of the cobalt film asdeposited on the substrate, e.g., by an amount in a range of from 25% to90% of the as-deposited resistivity of the cobalt film, in a range offrom 30% to 80% reduction, in a range of from 40% to 75% reduction, orin other range of reduction of resistivity, to yield a desiredresistivity value, e.g., a resistivity in a range of from 10 to 40μΩ-cm.

The cobalt film formed by processes of the present disclosure has highpurity and low resistivity, e.g., a resistivity in a range of from 7 to48 μΩ-cm, a range of from 10 to 45 μΩ-cm, a range of from 15 to 40μΩ-cm, a range of from 18 to 38 μΩ-cm, or resistivity in other suitablerange.

In specific embodiments of the process of the present disclosure, thecontacting of the precursor vapor with the substrate may be carried outwith delivery of the precursor vapor to the substrate at a suitable rateto achieve the desired deposited cobalt thickness and other properties.In specific embodiments, the precursor vapor maybe flowed to thesubstrate for contacting thereof, at a flow rate that is in a range offrom 20 to 200 μmoles/minute. The cobalt precursor may be flowed to thecontacting step in the mixture with hydrogen or other co-flow gas orgases. Such a co-flow gases may be delivered at any suitable rate, e.g.,a rate in a range of from 1 to 5 L per minute, or other suitable flowrate. The contacting may be carried out at pressure in a range of from10 to 50 torr in various specific embodiments. Cobalt may be depositedon the substrate from the precursor vapor at any suitable depositionrate, such as a deposition rate in a range of from 2 to 20 Å/minute, adeposition rate in a range of from 1 to 10 Å/minute, or other depositionrate.

The cobalt film in various embodiments of the present invention can beformed at any suitable thickness, e.g., a thickness in a range of from75 Å to 500 Å, a thickness in a range of from 10 Å to 400 Å, a thicknessin a range of from 20 Å to 300 Å, or thickness in another range.

The processes of the present disclosure may be carried out to producecobalt films of superior electrical character.

In specific embodiments of the process of the present disclosure, thecobalt precursor is volatilized to form the precursor vapor, and thecobalt film deposited on the substrate is annealed by a thermalannealing process. The thermal annealing process in such application maybe conducted for any suitable period of time and at any suitabletemperature. In illustrative embodiments, the annealing may be conductedfor a period of from 1 minute to two hours at temperature in a range offrom 150° C. to 500° C., e.g., or for a period of from 1 to 15 minutesat temperature in a range of from 375° C. to 450° C., or under othersuitable time and temperature conditions.

The cobalt films of the present disclosure as formed by methodcomprising the process according to any of the previously describedembodiments can be utilized to form devices comprising the high purity,low resistivity cobalt films. Such devices may be of any suitable type,and in various embodiments may comprise a semiconductor device,flat-panel display, or solar panel. The present disclosure thereforecontemplates a thin-film structure comprising a vapor-deposited highpurity, low resistivity cobalt film, such as a high purity, lowresistivity cobalt film formed by a method comprising a processaccording to any of the embodiments and aspects described hereinabove.

The present disclosure thus contemplates a process for forming cobalt ona substrate in which a cobalt precursor is volatilized to form precursorvapor that is contacted with the substrate under vapor depositionconditions effective for depositing cobalt on the substrate from theprecursor vapor. The deposited cobalt may be employed to fill a via ofthe substrate, with the cobalt being deposited over a copper surface inthe via. The copper surface may be at a lower portion or at a bottom ofthe via. The via may have a diameter in a range of from 15 nm to 45 nmin various embodiments, and in other embodiments may have a diameter ofless than 15 nm. The via may have an aspect ratio in a range of from 1:1to 5:1, and in a specific embodiment may have an aspect ratio of 3:1.

The copper surface in the via may have one or more layers depositedthereon, with the cobalt being deposited on an outermost surface of suchone or more layers. For example, the one or more layers may comprise alayer of tantalum on the copper surface, and a layer of tantalumnitride, wherein the outermost surface comprises surface of the layer oftantalum nitride. As another example, live one or more layers mayinclude a layer of ruthenium on the copper surface, a layer of tantalumon the layer of ruthenium, and a layer of tantalum nitride on the layerof tantalum, in which the outermost surface comprises surface of thelayer of tantalum nitride. As a still further example, the one or morelayers may include a layer of ruthenium on the copper surface, in whichthe outermost surface comprises surface of the layer of ruthenium.

The via fill process may be conducted with any suitable cobalt precursorfor the vapor deposition of cobalt, including the cobalt precursorsvariously described herein. The vapor deposition may comprise anysuitable vapor deposition technique, e.g., chemical vapor deposition(CVD).

The via fill process may be conducted in a dual-damascene structure, aspart of a corresponding process for semiconductor manufacturing. The viafill process may be conducted on a substrate from which a TiN hard maskhas been removed, as hereinafter more fully discussed. The cobalt in thevia fill method may in specific embodiments be deposited at temperaturenot exceeding about 200° C.

The disclosure correspondingly contemplates a void-free filled via asformed by a process described above.

In a further aspect, the disclosure relates to a process for formingcobalt on a substrate comprising metal-containing surface and oxidematerial surface, the process comprising contacting the substrate, undervapor deposition conditions effective for depositing cobalt on thesubstrate, with vapor of a cobalt precursor that is effective under thevapor deposition conditions to selectively deposit cobalt on themetal-containing surface of the substrate but not the oxide materialsurface of the substrate. As used in such context, the “metal-containingsurface” can contain any metal or any combination of metals, e.g.,alloys, as well as non-oxide compounds of such metals.

In such process for forming cobalt on a substrate comprisingmetal-containing surface and oxide material surface, themetal-containing surface can comprise metal selected from the groupconsisting of copper, tantalum, ruthenium, tungsten, aluminum, andcobalt. In specific embodiments, the metal-containing surface maycomprise a metal nitride, e.g., tantalum nitride. The oxide materialsurface may comprise dielectric material in various embodiments. Inspecific embodiments, the oxide material surface may comprise a siliconoxide material.

The cobalt precursor utilized in the foregoing process may be of anysuitable type(s), and may for example comprise a precursor selected fromthe group consisting of (i) cobalt bis-diazadiene compounds whosediazadiene moieties are optionally independently substituted on nitrogenand/or carbon atoms thereof with substituents selected from the groupconsisting of: H; C1-C8 alkyl; C6-C10 aryl; C7-C16 alkylaryl; C7-C16arylalkyl; halo; amines; amidinates; guanidinates; cyclopentadienyls,optionally substituted with C1-C8 alkyl, amines, or halo substituents;C1-C8 alkoxy; hydroxyl; oximes; hydroxyamines; acetates; carbonyls;beta-diketonates; and beta-ketoiminates; and (ii) cobalt compoundscontaining acetylenic functionality.

In the foregoing process for forming cobalt on a substrate comprisingmetal-containing surface and oxide material surface, the vapordeposition conditions in various embodiments comprise temperature notexceeding about 200° C. The vapor deposition in the foregoing processmay comprise chemical vapor deposition or any other suitable type ofvapor deposition.

The foregoing process may be carried out in various embodiments whereinthe substrate comprises copper surface and SiO₂ surface. In otherembodiments, the substrate comprises tantalum surface and and SiO₂surface. In still other embodiments, the substrate may comprise tantalumnitride surface and SiO₂ surface.

The advantages and features of the disclosure are further illustratedwith reference to the following examples, which is not to be construedas in any way limiting the scope of the disclosure but rather asillustrative of particular embodiments in specific implementationsthereof.

Example 1

Cobalt deposition selectivity was evaluated, using Co(tBUNCHCHNtBu)precursor, on silicon dioxide, copper, and ULK substrate surfaces, at“C”, “L”, and “BL” positions on the substrate surface. Initialdeposition runs were carried out at temperatures of 290° C., 250° C.,and 200° C., with the results shown in Table 1 below. Position “L”showed a lower deposition rate. Thickness of the deposited cobalt film,in Ångströms, was determined by x-ray fluorescence (XRF).

TABLE 1 Substrate Position Temperature (C.) XRF Thickness (A) SiO2 C 290113.8 Copper BL 290 230.4 SiO2 C 250 3.6 Copper L 250 121 ULK C 200 0Copper L 200 170

Next, selectivity was evaluated at temperature of 290° C., 250° C., 200°C., and 150° C., on silicon dioxide, copper, and ULK substrate surfaces,at “C”, “L”, and “BL” positions on the substrate surface usingCo(tBUNCHCHNtBu) precursor. The precursor flow rate was 50 μmole/minute,with hydrogen being flowed to the contacting operation at the rate of0.5 L per minute as a co-flow gas with the Co(tBuNCHCHNtBu) precursorvapor. The contacting operation was carried out at pressure of 30 torr.Deposition rate, in Angstroms per minute, of the cobalt film on thevarious substrate surfaces was determined, with the results shown inTable 2.

TABLE 2 Temperature Deposition Rate (° C.) Substrate Position (A/min)290 SiO₂ C 7.6 Cu BL 15.4 250 SiO₂ C 0.24 Cu CL 8.1 200 ULK C 0 L 0 Cu C11.7 L 11.3 150 ULK CB 0 L 0 Cu C 3.6 B 4.9

As reflected by the data at 200° C. and 150° C., the Co(BUNCHCHNtBu)precursor showed excellent selectivity at temperatures of ≤200° C.,depositing on copper surface but not on ULK surface on the substrate.

Example 2

The characteristics of Co(tBuNCHCHNtBu)₂, or Co(tBuDAD)₂, were evaluatedin a series of tests.

The thermogravimetric and differential scanning calorimetrycharacteristics of Co(tBuNCHCHNtBu)₂ were determined by correspondingTG/DSC analysis, generating the thermal characteristics plot shown inFIG. 1, showing a T₅₀ value of 221.9° C., and a residual mass value of0.2% at temperature of 772.3° C.

The Co(tBuNCHCHNtBu)₂ precursor then was evaluated in deposition onsilicon dioxide substrates, at the following deposition conditions: 290°C. deposition temperature; 50 μmole/minute delivery rate of theprecursor, deposition pressure of 10-30 torr; hydrogen as a co-reactantintroduced to the deposition chamber at flow rate of 0.5 to 3 L perminute; vaporizer temperature of 130° C.; and 90° C. deposition chambertemperature. The resulting deposited material was in the form of powderyCo₂C material. XRD analysis of such deposited Co₂C material identifiedsuch material has being orthorhombic in character, as shown by the XRDplot in FIG. 2.

A micrograph of the deposited Co₂C material, deposited at a cobaltthickness of 25.1 Å and pressure of 30 torr is shown in FIG. 3. Amicrograph of the deposited Co₂C material, deposited at a cobaltthickness of 69.7 Å and pressure of 30 torr is shown in FIG. 4. Amicrograph of the deposited Co₂C material, deposited at a cobaltthickness of 13.6 Å and pressure of 10 torr is shown in FIG. 5. Amicrograph of the deposited Co₂C material, deposited at a cobaltthickness of 59.3 Å and pressure of 10 torr is shown in FIG. 6.

The Co(tBuNCHCHNtBu)₂ precursor next was deposited on rutheniumsubstrates at temperature of 290° C. and precursor flow-rate of 50μmole/minute, with hydrogen as a co-flow gas delivered to the depositionchamber with the precursor. FIG. 7 is a micrograph of a cobalt filmformed on the ruthenium substrate at a deposition pressure of 10 torr.The thickness of the cobalt film was determined for this sample by x-rayfluorescence and scanning electron micrography, yielding anXRF-determined thickness of 16.6 nm, and an SEM-determined thickness of22 nm. The resistivity of the cobalt film was determined to be on theorder of 59 μΩ-cm.

Substrate effects were evaluated for the Co(tBuNCHCHNtBu)₂ precursordeposited that temperature of 290° C., pressure of 30 torr, and withflow of hydrogen as a co-reactant at flow rate of 0.5 L per minute. Theresults are shown in Table 3 below.

TABLE 3 Sheet R 290 C. Sheet R Dep Sheet R XRF Thickness Cal Sheet RResistivity Substrate (Ω/□) (Ω/□) (Ω/□) (A) (Ω/□) (μΩ-cm) XRD TaN 8.99.1 9.45 188.3 −246.38 −463.93 Ta 8.95 8.9 9.05 124.6 −526.61 −656.16TiN 40.2 44.2 37.78 180.1 260.11 468.45 Cu 0.22 0.19 0.20 230.4 −3.60−8.28 Amorphous PVD W 5.74 5.52 4.92 206.5 45.01 92.95 CVD W 0.43 0.4280.42 155.6 26.51 41.25 IrO2 29.85 27 14.49 204.1 31.27 63.83 Ru-2 9.58.6 6.99 163.4 37.31 60.96 FFW open open 43.94 208.7 43.94 91.70

Sheet resistance, in ohms/square, and resistivity in μΩ-cm, aretabulated in Table 3, along with cobalt film thickness in Ångströms, asdetermined by x-ray fluorescence, for a variety of substrates includingtantalum nitride, tantalum, titanium nitride, copper, tungsten depositedby physical vapor deposition, tungsten deposited by chemical vapordeposition, iridium dioxide, ruthenium, and fluorine free tungsten(FFW).

The effects of annealing on substrate resistivity were then determinedfor cobalt deposited from the Co(tBuNCHCHNtBu)₂ precursor on copper andruthenium substrates. Results are shown in FIG. 8, as a plot ofpercentage resistivity after annealing, as a function of annealingtemperature, in degrees Centigrade, for annealing carried out at apressure of 30 torr and hydrogen flow rate of 0.5 L per minute. Thepercentage of resistivity after annealing was a linear function ofannealing temperature, over the temperature range of from 200° C. to280° C.

FIG. 9 shows XRD plots for the cobalt films on tantalum nitride (uppertrace), titanium nitride (middle trace), and copper (lower trace)substrates, in intensity (arbitrary units) as a function of thetwo-theta angle, in degrees. This plot shows that cobalt was depositedon the copper substrate in an amorphous state.

FIG. 10 is an XRD plot of a cobalt film deposited from theCo(tBuNCHCHNtBu)₂ precursor on a tantalum nitride substrate, inarbitrary intensity units as a function of the two-theta angle, indegrees. The tantalum nitride substrate is shown as the lower trace inthis plot.

FIG. 11 is an XRD plot of a cobalt film deposited from theCo(tBuNCHCHNtBu)₂ precursor, in arbitrary intensity units as a functionof the two-theta angle, in degrees. The cobalt film trace on a fluorinefree tungsten (FFW) substrate in this plot is the upper trace, thecobalt film trace on an iridium substrate is the middle trace, and thecobalt film trace on a tantalum substrate is the lower trace.

FIG. 12 is an XRD plot of a cobalt film deposited from theCo(tBuNCHCHNtBu)₂ precursor on an iridium oxide substrate, in arbitraryintensity units as a function of the two-theta angle, in degrees. Theiridium oxide substrate is shown as the lower trace in this plot.

FIG. 13 is an XRD plot of a cobalt film deposited from theCo(tBuNCHCHNtBu)₂ precursor on a tantalum substrate, in arbitraryintensity units as a function of the two-theta angle, in degrees. Thetantalum substrate is shown as the lower trace in this plot.

FIG. 14 is an XRD plot of a cobalt film deposited from theCo(tBuNCHCHNtBu)₂ precursor on a ruthenium substrate, in arbitraryintensity units as a function of the two-theta angle, in degrees. Theruthenium substrate is shown as the lower trace in this plot.

FIG. 15 is a scanning electron micrograph of a cobalt film depositedfrom the Co(tBuNCHCHNtBu)₂ precursor on a tantalum substrate. The cobaltfilm had a thickness of 124.6 Å.

FIG. 16 is a scanning electron micrograph of a cobalt film on a coppersubstrate, at a cobalt film thickness of 230.4 Å.

FIG. 17 is a scanning electron micrograph of a cobalt film depositedfrom the Co(tBuNCHCHNtBu)₂ precursor on a tantalum nitride substrate,wherein the cobalt film had a thickness of 188.3 Å.

FIG. 18 is a scanning electron micrograph of a cobalt film depositedfrom the Co(tBuNCHCHNtBu)₂ precursor on a titanium nitride substrate,wherein the cobalt film had a thickness of 180.1 Å.

FIG. 19 is a scanning electron micrograph of a cobalt film depositedfrom the Co(tBuNCHCHNtBu)₂ precursor on a silicon substrate, wherein thecobalt film had a thickness of 25.3 Å.

FIG. 20 is a scanning electron micrograph of a cobalt film depositedfrom the Co(tBuNCHCHNtBu)₂ precursor on a fluorine free tungsten (FFW)substrate. The cobalt film thickness was 208.7 Å, and the film had aresistivity of 91.7 μΩ-cm.

FIG. 21 is a scanning electron micrograph, at 50,000× magnification, ofa cobalt film deposited from the Co(tBuNCHCHNtBu)₂ precursor on aniridium dioxide substrate. The cobalt film had a thickness of 204.1 Å.

FIG. 22 is a scanning electron micrograph, at 200,000× magnification, ofthe cobalt film of FIG. 23, deposited from the Co(tBuNCHCHNtBu)₂precursor on an iridium dioxide substrate, wherein the cobalt film had athickness of 204.1 Å.

Substrate effects were determined for cobalt films deposited from theCo(tBuNCHCHNtBu)₂ precursor on tantalum nitride, tantalum, copper,ruthenium, fluorine-free tungsten, and silicon dioxide substrates. Thecobalt film deposition was carried out at 250° C., pressure of 30 torr,and hydrogen co-reactant flow rate of 0.5 L per minute. The results areshown in Table 6 below.

TABLE 4 Sheet R 250 C. Sheet R Dep Sheet R XRF Thickness Cal Sheet RResistivity Substrate (Ω/□) (Ω/□) (Ω/□) (A) (Ω/□) (μΩ-cm) XRD TaN 0.8 Ta4.4 Cu 0.215 0.184 0.1974 121 −2.71 −3.3 Amorphous Ru-2 9.6 8.96 6.481205.1 23.42 48.0 FFW open open 60.74 127.4 60.74 77.4 SiO2 3.6

Resistivity and sheet resistance were evaluated for substrate effects,for cobalt films deposited from the Co(tBuNCHCHNtBu)₂ precursor oncopper, ruthenium, fluorine-free tungsten, and ultra-low dielectricconstant (ULK) material substrates. The deposition was carried out at200° C., pressure of 30 torr, and hydrogen co-reaction flow rate of 0.5L per minute. The results are shown in Table 7 below.

TABLE 5 Sheet R 200 C. Sheet R Dep Sheet R XRF Thickness Cal Sheet RResistivity Substrate (Ω/□) (Ω/□) (Ω/□) (A) (Ω/□) (μΩ-cm) XRD FFW openopen 31.5 FFW open open 30.7 Cu  0.2421 0.2324 0.2228 169.5 5.39 9.14Amorphous Ru-2 9.173 8.01 5.757 211.8 20.47 43.35 FFW open open open27.5 0 ULK 0 FFW open 10745000 60.1 6457745 FFW open 1832800 49.8 912734Cu  0.2142 0.186354 0.2228 349.9 −1.14 −4 Amorphous Ru-2 8.894 8.538244.255 396.8 8.48 34 FFW open open 11896000 50.3 5983688 ULK 0

FIG. 23 is an XRD plot of a cobalt film deposited from theCo(tBuNCHCHNtBu)₂ precursor on a ruthenium substrate, in arbitraryintensity units as a function of the two-theta angle, in degrees. Thelower line in this plot shows the data for deposition at 290° C., andcobalt film thickness of 166 Å. The middle line in this plot shows thedata for deposition at 250° C., and cobalt film thickness of 205.1 Å.The upper line in this plot shows the data for deposition at 200° C.,and cobalt film thickness of 211.8 Å.

FIG. 24 is a graph of resistivity, in μΩ-cm, as a function of filmthickness in Ångströms, as determined by x-ray fluorescence, for acobalt film deposited from the Co(tBuNCHCHNtBu)₂ precursor on aruthenium substrate, showing the data for deposition at a temperature of200° C., 250° C., and 290° C. The data show that the cobalt film had aresistivity on the order of 30 μΩ-cm.

FIG. 25 is an XRD plot of a cobalt film deposited from theCo(tBuNCHCHNtBu)₂ precursor on a fluorine-free tungsten substrate, inarbitrary intensity units as a function of the two-theta angle, indegrees. The upper line in this plot shows the data for deposition at290° C., and cobalt film thickness of 208.7 Å. The lower line in thisplot shows the data for deposition at 250° C., and cobalt film thicknessof 127.4 Å.

FIG. 26 is a graph of resistivity, in μΩ-cm, as a function of filmthickness in Ångströms, as determined by x-ray fluorescence, for acobalt film deposited from the Co(tBuNCHCHNtBu)₂ precursor on afluorine-free tungsten nitride substrate, at temperatures of 200° C.,250° C., and 290° C. The deposition was carried out at pressure of 30torr, and with hydrogen co-reactant flow rate of 0.5 L per minute.

FIG. 27 is a graph of resistivity, in μΩ-cm, as a function of filmthickness in Ångströms, as determined by x-ray fluorescence, for acobalt film deposited from the Co(tBuNCHCHNtBu)₂ precursor on afluorine-free tungsten nitride substrate, at a temperature of 250° C.,and precursor flow rate of 50 μmole/minute. A first run was carried outat pressure of 10 torr, and co-reactant hydrogen flow rate of 3 L perminute. A second run was carried out at pressure of 30 torr, andhydrogen co-reactant flow rate of 0.5 L per minute. A third run wascarried out at pressure of 30 torr, and hydrogen co-reactant flow rateof 3 L per minute. A fourth run was carried out at pressure of 10 torr,and hydrogen co-reactant flow rate of 0.5 L per minute.

The foregoing data showed that the bulk resistivity of the cobalt film,over a film thickness range of from 50 to 130 Å, was in a range of fromabout 75 μΩ-cm to about 150 μΩ-cm, at deposition temperature of 250° C.,deposition pressure of 30 torr, and 0.5 L per minute of hydrogenco-reactant flow.

FIG. 28 is a scanning electron micrograph of a cobalt film depositedfrom the Co(tBuNCHCHNtBu)₂ precursor on a fluorine-free tungstensubstrate, in which the film was deposited at temperature of 200° C.,pressure of 30 torr, co-reactant hydrogen flow of 0.5 L per minute,yielding a cobalt film thickness of 49.8 Å.

FIG. 29 is a scanning electron micrograph of a cobalt film depositedfrom the Co(tBuNCHCHNtBu)₂ precursor on a fluorine-free tungstensubstrate, in which the film was deposited at temperature of 250° C.,pressure of 10 torr, co-reactant hydrogen flow of 3 L per minute,yielding a cobalt film thickness of 39.8 Å, and film resistivity of 139μΩ-cm.

FIG. 30 is a scanning electron micrograph of a cobalt film depositedfrom the Co(tBuNCHCHNtBu)₂ precursor on a fluorine-free tungstensubstrate, in which the film was deposited at temperature of 250° C.,pressure of 30 torr, co-reactant hydrogen flow of 3 L per minute,yielding a cobalt film thickness of 35.8 Å, and a film resistivity of169 μΩ-cm.

FIG. 31 is a micrograph of a cobalt film deposited from theCo(tBuNCHCHNtBu)₂ precursor on a copper substrate, at depositiontemperature of 200° C., yielding a cobalt film thickness of 169.5 Å.

FIG. 32 is a micrograph of a cobalt film deposited from theCo(tBuNCHCHNtBu)₂ precursor on a copper substrate, at depositiontemperature of 150° C., yielding a cobalt film thickness of 97.6 Å.

Samples of the cobalt film deposited from the Co(tBuNCHCHNtBu)₂precursor on fluorine-free tungsten substrates at deposition temperatureof 250° C. were processed by 400° C. rapid thermal annealing in nitrogen(RTN), and the effect of such RTN processing on the sheet resistance andresistivity of the cobalt films was determined, with the results shownin Table 8 below.

TABLE 6 XRF 400 C 400 C RTN Thickness As dep AS dep RTN ResistivitySample ID (A) Sheet R R (μΩ · cm) Sheet R (μΩ · cm) 062514C-B 39.8 348.7138.8 215.4 85.7 062514C-CL 48.5 200.9 97.4 110.9 53.8 062614A-B 35.8471.4 168.8 185.4 66.4 062614A-CL 56.2 161.1 90.5 89.6 50.4

FIG. 33 is a graph of 400° C. RTN resistivity data for cobalt filmsdeposited from the Co(tBuNCHCHNtBu)₂ precursor (“Co(tBuDAD)₂) on afluorine-free tungsten substrate, and from other cobalt precursors onSiO₂ substrates, as a function of XRF-determined film thickness. Theadditional cobalt precursors were: dicobalt hexacarbonyltert-butylacetylene, which has the formula Co₂(CO)₆(HCC(CH₃)₃), with aboiling point of 52° C. at 0.8 torr (106.7 Pa), existing as a red liquidat 25° C. (CCTBA); high purity CCTBA (HP CCTBA); dicobalt hexacarbonyltrimethylsilyl acetylene (CCTMSA); cobalt carbonyl bis(trimethylsilylacetylene, having the formula [((H₃C)Si)C≡C]₂Co(CO) (CCBTMSA);bis(N-methylacetamidinato)cobalt (Co(Methyl-Amidinate)); andbis(N-ethylacetamidinato)cobalt (Co(Ethyl-Amidinate)).

The carbon content of cobalt films deposited from the Co(tBuNCHCHNtBu)₂precursor at varying temperature was determined for a series of samples.The deposition temperature in various runs was 150° C., 200° C., and250° C. The x-ray fluorescence (XRF) data are shown in Table 7 below,including the cobalt film thickness, in Ångströms, and the carboncontent of the film, in micrograms per square centimeter (μg/cm²). Theratio of carbon to cobalt in the film was determined, with the datashown in the table, in units of μg carbon/cm²/100 Ångströms of thecobalt film.

TABLE 7 Sample Dep Temp XRF XRF C/Co ID (° C.) Co (A) C (μg/cm2)(μg/cm2/100A) 071814A-CL 250 298.27 3.5911 1.204 071814A-CB 250 277.53.3689 1.214 072514A-CL 200 197.3 0.3495 0.177 072514B-CB 200 238.980.3734 0.156 072514C-CB 150 179.3 0.1546 0.086 082714C-CB 150 149.50.0977 0.065 082814A-CB 150 162 0.1504 0.093 090214A-CB 150 96.14 0.07230.075

The data in Table 7 shows that the carbon content of the cobalt film wassignificantly reduced at deposition temperature of 150° C., in relationto carbon content at deposition temperatures of 200° C. and 250° C.,with a greater than 15 times reduction in C/Co being shown for thedeposition temperature of 150° C., relative to the higher depositiontemperatures for which data were tabulated.

FIG. 34 is an XRD plot of a crystalline cobalt film deposited at 150° C.from the Co(tBuNCHCHNtBu)₂ precursor, in arbitrary intensity units, as afunction of the two-theta angle, in degrees.

FIG. 35 is a scanning electron micrograph of a cobalt film having athickness of 39.9 Å, which was deposited from the Co(tBuNCHCHNtBu)₂precursor on a substrate at a deposition rate of 150 μmoles per minute,at a pressure of 30 torr and a co-reactant hydrogen flow rate of 3 L perminute.

FIG. 36 is a scanning electron micrograph of a cobalt film having athickness of 13.4 Å, which was deposited from the Co(tBuNCHCHNtBu)₂precursor on a substrate at a deposition rate of 150 μmoles per minute,at a pressure of 10 torr and a co-reactant hydrogen flow rate of 3 L perminute.

The selective deposition of cobalt on copper in narrow via and trenchcavities of semiconductor substrates at relatively low temperatures witha low level of resultant defects in the cobalt has heretofore been quitechallenging. In such selective deposition in a via or a trench, it isdesirable to achieve homogeneous and complete filling with a smoothsurface (suppression of grain formation), and without deposition on lowk material and hard masks, particularly titanium nitride (TiN).

In such applications, it has surprisingly and unexpectedly beendiscovered that deposition of cobalt on copper can be achieved withremarkable diminution of defects that would otherwise be present in thedeposited cobalt; by pre-deposition treatment of the copper substratewith a cleaning composition comprising base and oxidizing agent havingpH in a range of from 5 to 10, and more preferably having pH in a rangeof greater than 7 up to 10.

In addition to significantly decreasing the formation of defects duringcobalt deposition in the via or trench, such pre-deposition cleaningtreatment can be used to pull back or even remove the TiN hard mask aswell as removing fluorocarbon (CF_(x)) polymers.

While the ensuing disclosure is primarily directed to pre-depositiontreatment of copper with the cleaning composition to enable subsequentdeposition of cobalt with reduced cobalt defectivity in relation tocorresponding deposition of cobalt without such pre-deposition cleaningtreatment, it is to be appreciated that the utility of thepre-deposition treatment method and associated cleaning composition isnot thus limited, but extends to pre-deposition cleaning of other metalsthan copper and subsequent deposition of other metals than cobalt. Forexample, the pre-deposition cleaning of tungsten for subsequentmetallization deposition is contemplated, in another aspect of thedisclosure.

The cleaning composition may be of any suitable type having thespecified components and pH characteristic, which is effective to effectreduction of defects in the cobalt deposited on copper, in relation tothe level of defects occurring in corresponding cobalt deposited on thecopper in the absence of pre-deposition treatment with the cleaningcomposition.

Cleaning compositions of a type described in International PatentApplication PCT/US2012/071777 filed Dec. 27, 2012, meeting the foregoingcriteria, may be usefully employed in the broad practice of the presentdisclosure to provide reduced defect cobalt on copper. The disclosure ofsuch International Patent Application PCT/US2012/071777 is herebyincorporated herein by reference in its entirety.

The pre-deposition cleaning of the copper on which cobalt is to bedeposited may be carried out in any suitable manner to effect contactingof the copper with the cleaning composition for a period of time that iseffective to achieve the diminution of defects in the deposited cobalt.Suitable contacting times may be empirically determined by varying thecontact time of the cleaning composition with copper samples followed bydeposition of cobalt, to determine appropriate contact times forachievement of deposited cobalt of a specific reduced defect character.In some embodiments, the cleaning composition may be contacted with thecopper for a period of 0.25 to 30 minutes, at temperature in a range offrom about 15° C. to about 100° C., although shorter or longer contacttimes and different temperature conditions may be necessary or desirablein other embodiments, depending on the character of the cleaningcomposition and the specific copper material that is being cleaned inthe pre-deposition cleaning operation.

Contacting of the cleaning composition with the copper may be carriedout in any suitable manner, and may in specific embodiments be affectedby immersion contacting, spray application of cleaning composition, mistor aerosol application, or any other suitable contacting method.

The contacting of the copper with the cleaning composition may befollowed with a rinse step in which the cleaned copper is rinsed withdeionized water or other solvent, to remove any residue front thecopper, to prepare it for the subsequent deposition of cobalt thereon.The cobalt deposition can then be carried out using a cobalt precursorof the present disclosure.

The base utilized in the cleaning composition may be of any suitabletype, and may in specific embodiments be selected from among: ammoniumhydroxide compounds of the formula NR₁R₂R₃R₄OH, wherein R₁, R₂, R₃, R₄may be the same as or different from one another and each isindependently selected from the group consisting of: hydrogen;straight-chained or branched C₁-C₆, alkyl groups (e.g., methyl, ethyl,propyl, butyl, pentyl, hexyl); C₁-C₆ alkoxy groups; C₁-C₆ hydroxyalkylgroups, (e.g., hydroxyethyl, hydroxypropyl); and substituted andunsubstituted aryl groups (e.g., benzyl); potassium hydroxide;tetrabutylphosphonium hydroxide (TBPH); 1,1,3,3-tetramethylguanidine(TMG); guanidine carbonate; arginine; monoethanolamine (MEA);diethanolamine (DEA); triethanolamine (TEA); ethylenediamine; cysteine;and combinations of the foregoing.

Specific base components of the foregoing types, as potentially usefulin cleaning compositions of the present disclosure, includetetramethylammonium hydroxide (TMAH), tetraethylammonium hydroxide(TEAH), tetrapropylammonium hydroxide (TPAH), tetrabutylammoniumhydroxide (TBAH), benzyltrimethylammonium hydroxide (BTMAH),benzyltriethylammonium hydroxide (BTEAH), (2-hydroxyethyl)trimethyiammonium hydroxide, (2-hydroxyethyl) triethylammoniumhydroxide, (2-hydroxyethyl) tripropylammonium hydroxide,(1-hydroxypropyl) trimethylammonium hydroxide, ethyltrimethylammoniumhydroxide, diethyldimethylammonium hydroxide (DEDMAH), and combinationsof two or more thereof.

The oxidizing agent employed in the cleaning composition may be of anysuitable type, and may in specific embodiments be selected from among:hydrogen peroxide: FeCl₃; FeF₃; Fe(NO₃)₃; Sr(NO₃)₂; CoF₃; MnF₃; oxone(2KHSO₅.KHSO₄.K₂SO₄); periodic acid: iodic acid; vanadium (V) oxide;vanadium (IV,V) oxide; ammonium vanadate; ammonium peroxomonosulfate:ammonium chlorite (NH₄ClO₂); ammonium chlorate (NH₄ClO₃); ammoniumiodate (NH₄IO₃); ammonium nitrate (NH₄IO₃); ammonium perborate (NH₄BO₃);ammonium perchlorate (NH₄ClO₄); ammonium periodate (NH₄IO₃); ammoniumpersulfate ((NH₄)₂S₂O₈); ammonium hypochlorite (NH₄ClO₄); ammoniumtungstate ((NH₄)₁₀H₂(W₂O₇); sodium persulfate (Na₂S₂O₈); sodiumhypochlorite (NaClO); sodium perborate; potassium iodate (KIO₃);potassium permanganate (KMnO₄); potassium persulfate; nitric acid(HNO₃); potassium persulfate (K₂S₂O₈); potassium hypochlorite (KCIO);tetramethylammonium chlorite ((N(CH₃)₄)ClO₂): tetramethylammoniumchlorate ((N(CH₃)₄)ClO₃); tetramethylammonium iodate ((N(CH₃)₄)IO₃);tetramethylammonium perborate ((N(CH₃)₄)BO₃): tetramethylammoniumperchlorate ((N(CH₃)₄)ClO₄); tetramethylammonium periodate((N(CH₃)₄)IO₄); tetramethylammonium persulfate ((N(CH₃)₄)S₂O₈);tetaabutylammonium peroxomonosulfate; peroxomonosulfuric acid; ferricnitrate (Fe(NO₃)₃); urea hydrogen peroxide ((CO(NH₂)₂)H₂O₂); peraceticacid (CH₃(CO)OOH); 1,4-benzoquinone; toluquinone;dimethyl-1,4-benzoquinone; chloranil; alloxan; N-methylmorpholineN-oxide; trimethylamine N-oxide: and combinations of two or more of theforegoing.

The cleaning composition may in specific embodiments further compriseone or more metal corrosion inhibitor components, e.g., metal corrosioninhibitor selected from the group consisting of5-amino-1,3,4-thiadiazole-2-thiol (ATDT), benzotriazole (BTA),1,2,4-triazole (TAZ), tolytriazole, 5-methyl-benzotriazole,5-phenyl-benzotriazole, 5-nitro-benzotriazole, benzotriazole carboxylicacid, 3-amino-5-mercapto-1,2,4-triazole, 1-amino-1,2,4-triazole,hydroxybenzotriazole, 2-(5-amino-pentyl)-benzotriazole,1-amino-1,2,3-triazole, 1-amino-5-methyl-1,2,3-triazole,3-amino-1,2,4-triazole, 3-mercapto-1,2,4-triazole,3-isopropyl-1,2,4-triazole, 5-phenylthiol-benzotriazole,halo-benzotriazoles (halo=F, Cl, Br or I), naphthotriazole,2-mercaptobenzimidazole (MBI), 2-mercaptobenzothiazole,4-methyl-2-phenylimidazole, 2-mercaptothiazoline, 5-aminotetrazole,pentylenetetrazole, 5-phenyl-1H-tetrazole, 5-benzyl-1H-tetrazole,Ablumine O, 2-benzylpyridine, succinimide,2,4-diamino-6-methyl-1,3,5-triazine, thiazole, triazine,methyltetrazole, 1,3-dimethyl-2-imidazolidmone,1,5-pentamethylenetetrazole, 1-phenyl-5-mercaptotetrazole,diaminomethyltriazine, imidazoline thione,4-methyl-4H-1,2,4-mazole-3-thiol, benzothiazole, imidazole, indiazole,adenosine, carbazole, saccharin, benzoin oxime, PolyFox PF-159,poly(ethylene glycol), poly(propylene glycol), PEG-PPG copolymers,dodecylbenzenesulfonic acid, benzalkonium chloride,benzyldimethyidodecylammonium chloride, myristyltrimethylammoniumbromide, dodecyltrimethylammonium bromide, hexadecylpyridinium chloride,Aliquat 336, benzyldimethylphenylammonium chloride, Crodaquat TES,Rewoquat CPEM, hexadecyltrimethylammonium p-toluenesulfonate,hexadecyltrimethylammonium hydroxide,1-methyl-1′-tetradecyl-4,4′-bipyridium dichloride,alkyltrimethylammonium bromide, amprolium hydrochloride, benzethoniumhydroxide, benzethonium chloride, benzyldimethylhexadceylammoniumchloride, benzyldimethyltetradceylammonium chloride,benzyldodecyldimethylammonium bromide, benzyldodecyldimethylammoniumchloride, cetylpyridinium chloride, choline p-toluenesulfonate salt,dimethyldioctadecylammonium bromide, dodecylethyldimcthylammoniumbromide, dodecyltrimethylammonium chloride,ethylhexadecyldimethyiammonium bromide, Girard's reagent,hexadecyl(2-hydroxyethyl)dimethylammonium dihydrogen phosphate,dexadecylpyridinium bromide, hexadecyltrimethylammonium bromide,hexadecyltrimethylammonium chloride, methylbenzethonium chloride,Hyamine® 1622, Luviquat™, N,N′,N′-polyoxyethylene(10)-N-tallow-1,3-diaminopropane liquid, oxyphenonium bromide,tetraheptylammonium bromide, tetrakis(decyl)ammonium bromide, thonzoniumbromide, tridodecylammonium chloride, trimethyloctadecylammoniumbromide, 1-methyl-3-n-octylimidazolium tetrafluoroborate,1-decyl-3-methylimidazolium tetrafluoroborate.1-decyl-3-methylimidazolium chloride, tridodecylmethylammonium bromide,dimethyldistrearylammonium chloride, hexamethonium chloride, andcombinations of two or more of the foregoing.

In particular embodiments, the cleaning composition may additionallycomprise oxidizing agent stabilizer, as for example stabilizer selectedfrom among glycine, serine, proline, leucine, alanine, asparagine,aspartic acid, glutamine, valine, and lysine, oitrilotriacetic acid,iminodiacetic acid, etidronic acid, ethylenediaminetetraacetic acid(EDTA), (1,2-cyclohexylenedinitrilo)tetraacctic acid (CDTA), uric acid,tetraglyme, diethylenctriamine pentaacetic acid, propylenediaminetetraacetic acid, ethylendiamine disuccinic acid, sulfanilamide, andcombinations of two or more of the foregoing.

The cleaning composition can be formulated to comprise any of varioussuitable solvents, as for example, water, water-miscible organicsolvents, and combinations of the foregoing. Water-miscible organicsolvents that may be usefully employed in specific cleaning compositionsinclude those of the formula R¹R²R³C(OH), where R¹, R² and R³ areindependent from each other and are selected from to the groupconsisting of hydrogen, C₂-C₃₀alkyls, C₂-C₃₀alkenes, cycloalkyls,C₂-C₃₀alkoxys, and combinations thereof.

Specific solvents that may be usefully employed in specific embodimentsinclude those selected from the group consisting of water, methanol,ethanol, isopropanol, butanol, pentanol, hexanol, 2-ethyl-1-hexanol,heptanol, octanol, ethylene glycol, propylene glycol, butylene glycol,butylene carbonate, ethylene carbonate, propylene carbonate, dipropyleneglycol, diethylene glycol monomethyl ether, triethylene glycolmonomethyl ether, diethylene glycol monoethyl ether, triethylene glycolmonoethyl ether, ethylene glycol monopropyl ether, ethylene glycolmonobutyl ether, diethylene glycol monobutyl ether, triethylene glycolmonobutyl ether, ethylene glycol monohexyl ether, diethylene glycolmonohexyl ether, ethylene glycol phenyl ether, propylene glycol methylether, dipropylene glycol methyl ether (DPGME), tripropylene glycolmethyl ether (TPGME), dipropylene glycol dimethyl ether, dipropyleneglycol ethyl ether, propylene glycol n-propyl ether, dipropylene glycoln-propyl ether (DPGPE), tripropylene glycol n-propyl ether, propyleneglycol n-butyl ether, dipropylene glycol n-butyl ether, tripropyleneglycol n-butyl ether, propylene glycol phenyl ether,2,3-dihydrodecafluoropentane, ethyl perfluorobutylether, methylperfluorobutylether, alkyl carbonates, alkylene carbonates,4-methyl-2-pentanol, and combinations of two or more of the foregoing.

In specific embodiments, the solvent may comprise water, such asdeionized water.

In cleaning compositions in which water is employed as a solvent, theamount of water in the composition may be of a suitable amount that iseffective to enable the composition to achieve its intended purpose ofreducing defects in the cobalt deposited on the copper that is cleanedwith such composition. The cleaning composition may for example comprisewater in an amount of from 65 wt % to 95 wt % or more, based on thetotal weight of the cleaning composition.

In specific embodiments, the cleaning composition may comprise anaqueous composition including from 0.1 wt % to 10 wt % base, and from 5wt % to 40 wt % oxidizing agent, based on total weight of the cleaningcomposition.

In various embodiments, the cleaning composition may be provided in theform of a cleaning composition concentrate that then is diluted orotherwise mixed with solvent and/or other components to constitute thefinal cleaning composition for use. In this respect, the oxidizing agentmay be absent from the concentrate, to avoid issues of instability ofthe oxidizing agent when the concentrate is stored for a significantperiod of time, and the concentrate may be mixed with the oxidizingagent at the point of use, e.g., in a semiconductor manufacturingfacility.

In specific implementations, the cleaning composition may comprise anyother suitable components, such as surfactants, dielectric passivatingagents, stabilizers, dispersing or suspending agents, etc.

The cleaning composition and pre-deposition cleaning method of thepresent disclosure are highly effective in achieving substantialreduction of defects in deposited metal that is deposited on othermetals in semiconductor substrate cavities such as vias and trenches.This is shown in FIGS. 37 and 38.

FIG. 37 is an electron micrograph at a magnification of 25,000 times,showing a cobalt film that has been deposited on copper that has notbeen cleaned by a pre-deposition cleaning with the cleaning compositionof the present disclosure. The resulting cobalt film exhibits manydefects, as is readily visually apparent from such micrograph.

FIG. 38 is an electron micrograph at a magnification of 25,000 times,showing a cobalt film that has been deposited on copper that has beencleaned with a cleaning composition of the present disclosure,comprising an approximate weight percentage composition of 89% deionizedwater, 9% oxidizing agent, and 2% base, based on total weight of thecleaning composition, as contacted with the copper for 2 minutes at 50°C. The resulting cobalt film deposited on such cleaned copper, as shownin FIG. 38, exhibits few visual defects (<1%).

A comparison of FIGS. 37 and 38 shows the striking reduction in cobaltfilm defects that has been achieved by the cleaning method andcomposition of the present disclosure.

In another aspect, the disclosure relates to a method of reducingdefects in a deposited metal that is vapor deposited on a base metal,such method comprising cleaning the base metal, prior to vapordeposition of the deposited metal thereon, with a cleaning compositioncomprising etchant, oxidizing agent, and optionally corrosion inhibitor,having pH in a range of from 0 to 4. Such method may be conducted with abase metal such as tungsten, or other suitable metal. The compositionmay be substantially devoid of hydrogen peroxide, and may be variouslyconstituted with suitable etchant species.

In various embodiments, the etchant may comprise a species selected fromthe group consisting of H₂ZrF₆, H₂TiF₆, HPF₆, HF, ammonium fluoride,tetrafluoroboric acid, hexafluorosilicic acid, tetrabutylammoniumtetrafluoroborate (TBA-BF₄), ammonium hexafluorosilicate, ammoniumhexafluorotitanate, tetraalkylaminonium fluoride (NR₁R₂R₃R₄F),tetraalkylammonium hydroxide (NR₁R₂R₃R₄OH), where R₁, R₂, R₃, R₄ may bethe same as or different from one another and each is independentlyselected from the group consisting of straight-chained or branched C₁-C₆alkyl groups, weak bases, and combinations thereof.

In other embodiments, the etchant may comprise tetrafluoroboric acid orhexafluorosilicic acid.

In the preceding method involving a cleaning composition having pH in arange of from 0 to 4, the oxidizing agent may be of any suitable typeand may for example comprise a species selected from the groupconsisting of FeCl₃ (both hydrated and unhydrated), Fe(NO₃)₃, Sr(NO₃)₂,CoF₃, FeF₃, MnF₃, oxone (2KHSO₅.KHSO₄.K₂SO₄), periodic acid, iodic acid,vanadium (V) oxide, vanadium (IV,V) oxide, ammonium vanadate, ammoniumperoxomonosulfate, ammonium chlorite (NH₄ClO₂), ammonium chlorate(NH₄ClO₃), ammonium iodate (NH₄IO₃), ammonium nitrate (NH₄NO₃) ammoniumperborate (NH₄BO₃), ammonium perchlorate (NH₄ClO₄), ammonium periodate(NH₄IO₃), ammonium persulfate ((NH₄)₂S₂O₈), ammonium hypochlorite(NH₄ClO), ammonium tungstate ((NH₄)₁₀H₂(W₂O₇)), sodium persulfate(Na₂S₂O₈), sodium hypochlorite (NaClO), sodium perborate, potassiumiodate (KIO₃), potassium permanganate (KMnO₄), potassium persulfate,nitric acid (HNO₃), potassium persulfate (K₂S₂O₈), potassiumhypochlorite (KClO), tetramethylammonium chlorite ((N(CH₃)₄)ClO₂),tetramethylammonium chlorate ((N(CH₃)₄)ClO₃), tetramethylammonium iodate((N(CH₃)₄)IO₃), tetramethylammonium perborate ((N(CH₃)₄)BO₃),tetramethylammonium perchlorate ((N(CH₃)₄)ClO₄), tetramethylammoniumperiodate ((N(CH₃)₄)IO₄), tetramethylammonium persulfate((N(CH₃)₄)S₂O₈), tetrabutylammonium peroxomonosulfate,peroxomonosulfuric acid, ferric nitrate (Fe(NO₃)₃), peracetic acid(CH₃(CO)OOH), 1,4-benzoquinone, toluquinone, dimethyl-1,4-benzoquinone,chloranil, alloxan, N-methylmorphine N-oxide, trimethylamine N-oxide,and combinations thereof.

In other embodiments of the method involving a cleaning compositionhaving pH in a range of from 0 to 4, the oxidizing agent may comprise aspecies selected from the group consisting of vanadium oxide, ammoniumiodate, ammonium periodate, ammonium vanadate, periodic acid, iodicacid, and 1,4-benzoquinone. In still other embodiments, the oxidizingagent in the cleaning composition may comprise a species selected fromthe group consisting of ammonium iodate, ammonium periodate, iodic acid,and periodic acid.

The cleaning composition having pH in a range of from 0 to 4 may beconstituted as comprising at least one iodine scavenger, such as aniodine scavenger comprising a ketone.

In other embodiments, the iodine scavenger may be selected from thegroup consisting of 4-methyl-2-pentanone, 2,4-dimethyl-3-pentanone,cyclohexanone, 5-methyl-3-heptanone, 3-pentanone, 5-hydroxy-2-pentanone,2,5-hexanedione, 4-hydroxy-4-methyl-2-pentanone, acetone, butanone,2-methyl-2-butanone, 3,3-dimethyl-2-butanont 4-hydroxy-2-butanone,cyclopentanone, 2-pentanone, 3-pentanone, 1-phenylethanone,acetophenone, benzophenone, 2-hexatone, 3-hexatone, 2-heptanone,3-heptanone, 4-heptanone, 2,6-dimethyl-4-heptanone, 2-octanone,3-octanone, 4-octanone, dicyclohexyl ketone, 2,6-dimethylcyclohexanone,2-acetylcyclohexanone, 2,4-pentanedione, menthone, and combinationsthereof.

In still other embodiments, the iodine scavenger may be selected fromthe group consisting of 4-methyl-2-pentanone, 2,4-dimethyl-3-pentanone,and cyclohexanone.

The cleaning composition having pH in a range of from 0 to 4 may furthercomprise a solvent, such as water, e.g., to constitute a compositioncomprising at least 98 wt % water, based on total weight of thecomposition.

The cleaning composition having pH in a range of from 0 to 4 maycomprise a suitable corrosion inhibitor, such as a corrosion inhibitorcomprising a species selected from the group consisting of5-amino-1,3,4-thiadiazole-2-thiol (ATDT), benzotriazole (BTA),1,2,4-triazole (TAZ), tolyltriazole, 5-methyl-benzotriazole,5-phenyl-benzotriazole, 5-nitro-benzotriazole, benzotriazole carboxylicacid, 3-amino-5-mercapto-1,2,4-triazole, 1-amino-1,2,4-triazole,hydroxybenzotriazole, 2-(5-amino-pentyl)-benzotriazole,1-amino-1,2,3-triazole, 1-amino-5-methyl-1,2,3-triazole,3-amino-1,2,4-triazole, 3-mercapto-1,2,4-triazole,3-isopropyl-1,2,4-triazole, 5-phenylthiol-benzotriazole,halo-benzotriazoles (halo=F, Cl, Br or I), naphthotriazole,2-mercaptobenzimidazole (MBI), 2-mercaptobenzothiazole,4-methyl-2-phenylimidazole, 2-mercaptothiazoline, 5-aminotetrazole,pentylenetetrazole, 5-phenyl-1H-tetrazole, 5-benzyl-1H-tetrazole,Ablumine O, 2-benzylpyridine, succinimide,2,4-diamino-6-methyl-1,3,5-triazine, thiazole, triazine,methyltetrazole, 1,3-dimethyl-2-imidazolidinone,1,5-pentamethylenetetrazole, 1-phenyl-5-mercaptotetrazole,diaminomethyltriazine, imidazoline thione,4-methyl-4H-1,2,4-triazole-3-thiol, benzothiazole, imidazole, indiazole,adenosine, carbazole, saccharin, benzoin oxime, PolyFox PF-159,poly(ethylene glycol), poly (propylene glycol), PEG-PPG copolymers,dodecylbenzenesulfonic acid, sodium dodecylbenzenesulfonate, andcombinations thereof.

In other embodiments, the corrosion inhibitor may comprise a cationicquaternary species selected from the group consisting of cationicquaternary salts such as benzalkonium chloride,benzyldimethyldodecylammonium chloride, myristyltrimethylammoniumbromide, dodecyltrimethylammonium bromide, hexadecylpyridinium chloride,Aliquat 336, benzyldimethylphenylammonium chloride, Crodaquat TES,Rewoquat CPEM, hexadecyltrimethylammonium p-toluenesulfonate,hexadecyltrimethyiammonium hydroxide,1-methyl-1′-tetradecyl-4,4′-bipyridium dichloride,alkyltrimethylammonium bromide, amprolium hydrochloride, benzethoniumhydroxide, benzethonium chloride, benzyldimethylhexadecylammoniumchloride, benzyldimethyltetradecylammonium chloride,benzyldodecyldimethylammonium bromide, benzyldodecyldimedrylammoniumchloride, cetylpyridinium chloride, choline p-toluenesulfonate salt,dimethyldioctadecylammonium bromide, dodecylethyldimethylammoniumbromide, dodecyltrimethylammonium chloride,ethylhexadecyldimethylammonium bromide, Girard's reagent,hexadecyl(2-hydroxyethyl)dimethylammonium dihydrogen phosphate,dexadceylpyridinium bromide, hexadecyltrimethylammonium bromide,hexadecyltrimethylammonium chloride, methylbenzethonium chloride,Hyamine® 1622, Luviquat™, N,N′,N′-polyoxyethylene(10)-N-tallow-1,3-diaminopropane liquid, oxyphenonium bromide,tetraheptylammonium bromide, tetrakis(decyl)ammonium bromide, thonzoniumbromide, tridodecylammonium chloride, trimethyloctadecylammoniumbromide, 1-methyl-3-n-octylimidazolium tetrafluoroborate,1-decyl-3-methoylimidazolium tetrafluoroborate,1-decyl-3-methylimidazoliutn chloride, tridodecylmethylammonium bromide,dimethyldistearylammonium chloride, and hexamethonium chloride.

The cleaning composition having pH in a range of from 0 to 4 may also beconstituted as comprising at least one additional component selectedfrom the group consisting of surfactants, low-k passivating agents,silicon-containing compounds, and combinations thereof. The passivatingagent may comprise a passivating agent selected from the groupconsisting of boric acid, ammonium pentaborate, sodium tetraborate,3-hydroxy-2-naphthoic acid, malonic acid, iminodiacetic acid, andcombinations thereof. The silicon-containing compound(s) may be selectedfrom the group consisting of methyltrimethoxysilane,dimethyldimethoxysilane, phenyltrimethoxysilane, tetracthoxysilane(TEOS), N-propyltrimethoxysilane, N-propyltriethoxysilane,hexyltrimethoxysilane, hexyltriethoxysilane, ammoniumhexaflurorosilicate, sodium silicate, tetramethyl ammonium silicate(TMAS), and combinations thereof.

The cleaning composition having pH in a range of from 0 to 4 may invarious embodiments be substantially devoid of amines, abrasivematerials, chloride sources, metal halides, and combinations thereof.

The disclosure in a further aspect relates to a method of reducingdefects in a deposited cobalt that is vapor deposited on a base metal,wherein the cobalt is deposited by a process of the present disclosure,such method comprising cleaning the base metal, prior to vapordeposition of the deposited cobalt thereon, wherein the cleaningcomprises (i) contacting the base metal with a cleaning compositioncomprising base and oxidizing agent, having pH in a range of from 5 to10; (ii) contacting the base metal with a cleaning compositioncomprising etchant, oxidizing agent, and optionally corrosion inhibitor,having pH in a range of from 0 to 4; (iii) treating the base metal withhydrogen plasma; or (iv) treating the base mewl with hydrogen fluoride.

In another aspect, the disclosure relates to a method of formingdeposited cobalt on a substrate, wherein prior to vapor deposition ofcobalt on the substrate, the substrate is cleaned with a cleaningcomposition selected from among (i) cleaning compositions comprisingbase and oxidizing agent, having pH in a range of from 5 to 10, and (ii)cleaning compositions comprising etchant, oxidizing agent, andoptionally corrosion inhibitor, having pH in a range of from 0 to 4,wherein the cleaning of the substrate is effective for at least one of(a) reducing defectively of the deposited cobalt, (b) removing CF_(X)components from the substrate, and (c) removing or pulling back TiNpresent on the substrate. Such method may be carried out for highlyeffective deposition of cobalt on substrates such as copper substratesand tungsten substrates.

Another aspect of the disclosure relates to selective growth of cobalton copper and selective growth of cobalt on barrier and liner materialsthat are in turn deposited on copper, in the achievement of void-freevia fills. As discussed in the background section hereof, semiconductormanufacturing technology faces challenges in reducing interconnect lineresistance and achieving high-yield void-free fill in vias in whichcopper is present and Ta, TaN, Ru, and Ru alloys may be employed, incopper-diffusion barriers and liners in the via.

The present disclosure contemplates cobalt deposition to achievevoid-free via fills in small size vias, e.g. in dual-damascenestructures and processes, in various embodiments, the void free viafills of the present disclosure may be carried out in vias havingcritical dimensions of from 15 nm to 45 nm, with aspect ratios of from1:1 to 5:1, e.g., in a range of from 1.5:1 to 4.5:1, or a range of from2:1 to 4:1, or an aspect ratio of 3:1.

In such via fills, cobalt may be vapor deposited in the via directly oncopper therein, or on material that in turn is deposited on copper,e.g., a barrier or liner material comprising any one or more oftantalum, tantalum nitride, ruthenium, and ruthenium alloys. Forexample, the cobalt may be deposited, by CVD or other vapor depositionprocess, in the via on any of the following combinations of layers(where copper is the bottom layer in such layer sequence, and cobalt isdeposited on the last material layer in the sequence): Cu/Ta/TaN:Cu/Ru/Ta/TaN; and Cu/Ru.

The disclosure further contemplates vapor deposition of cobalt onanother layer of cobalt, in successive separate vapor depositionoperations, in various embodiments of the disclosure.

The disclosure thus also contemplates implementations in which thedeposited cobalt forms an interconnect line or a core of an interconnectline in the via, so that the cobalt forms the core of the via, and docsnot serve only as a cap, barrier, or liner.

The deposition of cobalt for selective growth on copper to achievevoid-free via fills is achieved in accordance with the presentdisclosure, using cobalt precursors such as those described herein, invapor deposition processes, e.g., chemical vapor deposition (CVD).

A cobalt process can be conducted in which cobalt only selectivelynucleates and grows on a copper surface at the bottom of a via to form abottom-up fill of the via. This approach can be used in chemical vapordeposition processes, or other vapor deposition processes, for selectivegrowth of cobalt to fill vias of very challenging dimensions. The viafill with cobalt can be followed by another interconnect metal fill ofthe lines in a dual-damascene structure.

By way of example, cobalt deposition was carried out using a dualdamascene test structure as shown in FIG. 39, in which vias are filledwith copper in a lower portion of the structure, and copper in some ofsuch vias is exposed to upper section vias in a layer of SiO₂ on which atitanium nitride (TiN) hard mask layer has been formed. The vias had adiameter of 45 nm and a 3:1 aspect ratio.

FIG. 40 is a top view micrograph of the via test structure, and FIG. 41is a cross-sectional view of the test structure, prior to cobaltselective growth and fill.

Cobalt depositions were performed on the test structures, both with andwithout removal of the TiN hard mask prior to cobalt deposition. In bothcases, cobalt deposition was performed at temperature of approximately200° C. in a 300 mm wafer CVD deposition system.

FIG. 42 is a scanning electron micrograph (SEM) of the cross-section ofthe cobalt filled via structure, in which cobalt completely fills the˜135 nm tall and 45 nm diameter (3:1 aspect ratio) via structure. FIG.43 is an SEM top view of the cobalt filled via, in which the cobaltdeposition was carried out after the TiN hard mask w as removed. Therewas no deposition of cobalt in the area w here no copper presented(i.e., the area of the SiO₂ dielectric), and cobalt deposition onlynucleated inside the via where the bottom was the exposed coppersurface. This cobalt via fill thus provided highly selective growth ofcobalt on the copper in the via, to effect the via fill.

Comparative deposition of cobalt on wafers in which the TiN hard maskwas retained exhibited a significantly higher level defects than whensuch mask was removed, and the defect areas included various sizes ofvoids, in contrast to the cobalt fill that was carried out when the TiNhard mask had been removed prior to cobalt deposition. Such resultsindicate the advantage of removing the TiN hard mask prior to cobaltselective deposition being conducted.

When cobalt is grown inside a via, the growth is confined by the via andnucleation occurs on the growing surface. When growth of the cobaltpasses the top of the via and there is excess growth lime, cobalt maynucleate on the sides of the cobalt external to the via and inconsequence growth may occur in a lateral direction as well as an upwarddirection and form exterior “cauliflower”-like overgrowths. Suchovergrowths may be acceptable within the overall structure of thedevice, or the overgrowth or portions thereof may be removed byappropriate etch or planarization techniques.

Scanning transmission electron microscope (STEM) images show that cobaltdeposited in vias by the above-described fill process isnano-crystalline or nearly amorphous in nature, when growth temperatureson the order of 200° C. were employed. The grain size of the depositedcobalt in such fill process was estimated to be less than 10 nm,reflecting compatibility of the bottom-up fill of cobalt in vias beyondthe 14 nm node.

While the disclosure has been set forth herein in reference to specificaspects, features and illustrative embodiments, it will be appreciatedthat the utility of the disclosure is not thus limited, but ratherextends to and encompasses numerous other variations, modifications andalternative embodiments, as will suggest themselves to those of ordinaryskill in tire field of the present disclosure, based on the descriptionherein. Correspondingly, the disclosure as hereinafter claimed isintended to be broadly construed and interpreted, as including ail suchvariations, modifications and alternative embodiments, within its spiritand scope.

What is claimed is:
 1. A surface-selective deposition process fordepositing cobalt on a having a copper surface, comprising: cleaning thecopper surface with an acid solution prior to vapor deposition of thedeposited cobalt on the substrate, the acid solution having pH in arange of from 0 to 4; cleaning the copper surface with a cleaningsolution prior to vapor deposition of the deposited cobalt on thesubstrate, the cleaning solution comprising base and an oxidizing agentand having a pH in a range of from 5 to 10; volatilizing anon-oxygen-containing cobalt precursor to form a precursor vapor,wherein the non-oxygen-containing cobalt precursor comprises a cobaltbis-diazadiene compound whose diazadiene moieties are optionallyindependently substituted on nitrogen and/or carbon atoms thereof withsubstituents selected from the group consisting of: H; C₁-C₈ alkyl;C₆-C₁₀ aryl; C₇-C₁₆ alkylaryl; C₇-C₁₆ arylalkyl; halo; amines;amidinates; guanidinates; and cyclopentadienyls, optionally substitutedwith C₁-C₈ alkyl, amines, or halo substituents; and contacting theprecursor vapor with the substrate under vapor deposition conditionseffective for depositing cobalt on the substrate from the precursorvapor, wherein the vapor deposition conditions include temperature notexceeding 200° C., and wherein the substrate includes copper surface anddielectric material surface and wherein cobalt is deposited selectivelyon the copper surface relative to the dielectric material.
 2. Theprocess of claim 1, wherein the non-oxygen-containing cobalt precursorcomprises a precursor selected from the group consisting of cobaltbis-diazadiene compounds whose diazadiene moieties are optionallyindependently substituted on nitrogen and/or carbon atoms thereof withsubstituents selected from the group consisting of: H; C₁-C₈ alkyl;C₆-C₁₀ aryl; C₇-C₁₆ alkylaryl; C₇-C₁₆ arylalkyl; halo; amines;amidinates; guanidinates; and cyclopentadienyls, optionally substitutedwith C₁-C₈ alkyl, amines, or halo substituents.
 3. The process of claim1, wherein the non-oxygen-containing cobalt precursor comprises aprecursor selected from the group consisting of cobalt bis-diazadienecompounds whose diazadiene moieties are optionally independentlysubstituted on nitrogen and/or carbon atoms thereof with substituentsselected from the group consisting of: H; C₁-C₈ alkyl; C₆-C₁₀ aryl;C₇-C₁₆ alkylaryl; C₇-C₁₆ arylalkyl; halo; amines; amidinates;guanidinates; and cyclopentadienyls, optionally substituted with C₁-C₈alkyl, amines, or halo substituents.
 4. The process of claim 1, whereinthe non-oxygen-containing cobalt precursor comprises:


5. The process of claim 1, wherein the non-oxygen-containing cobaltprecursor comprises a cobalt precursor of the formula {RNCHCHNR}₂Co, or{R′NCRCRNR′}₂Co, wherein each R and R′ is independently selected fromamong C₁-C₈ alkyl.
 6. The process of claim 1, wherein the precursorvapor is mixed with hydrogen for said contacting.
 7. The process ofclaim 1, further comprising annealing the cobalt deposited on thesubstrate.
 8. The process of claim 1, wherein the non-oxygen-containingcobalt precursor comprises a cobalt precursor with mono- orbis-substituted alkyl-1,3-diazabutadienyl ligands.
 9. The process ofclaim 1, wherein the deposited cobalt forms an electrode.
 10. Theprocess of claim 1, wherein said vapor deposition conditions comprise adeposition pressure in a range of from 2 to 1200 torr.
 11. The processof claim 1, further comprising annealing the cobalt deposited on thesubstrate by thermal annealing at temperature in a range of from 200° C.to 600° C.
 12. The process of claim 1, wherein said contacting of theprecursor vapor with the substrate is carried out for a period of timesufficient to deposit cobalt on the substrate at a thickness in a rangeof from 2 nm to 1000 nm.
 13. The process of claim 1, wherein the cobaltdeposited on the substrate has a resistivity in a range of from 7 to 48μΩ-cm.
 14. The process of claim 1, wherein the deposited cobalt fills avia of the substrate and is deposited over the copper surface in thevia.
 15. The process of claim 1, wherein the copper surface has one ormore layers deposited thereon, and said cobalt is deposited on anoutermost surface of said one or more layers.
 16. The process of claim1, wherein the vapor deposition conditions include temperature in arange of from 120° C. to 175° C.